CS80C286-16

DATASHEET 80C286 FN2947 Rev.3.00 January 28, 2008 High Performance Microprocessor with Memory Management and Protection Features Description • Compatible with NMOS 80286 • Wide Range of Clock Rates - DC to 25MHz (80C286-25) - DC to 20MHz (80C286-20) - DC to 16MHz (80C286-16) - DC to 12.5MHz (80C286-12) - DC to 10MHz (80C286-10) • Static CMOS Design for Low Power Operation - ICCSB = 5mA Maximum - ICCOP = 185mA Maximum (80C286-10) 220mA Maximum (80C286-12) 260mA Maximum (80C286-16) 310mA Maximum (80C286-20) 410mA Maximum (80C286-25) • High Performance Processor (Up to 19 Times the 8086 Throughput) • Large Address Space • 16 Megabytes Physical/1 Gigabyte Virtual per Task • Integrated Memory Management, Four-Level Memory Protection and Support for Virtual Memory and Operating Systems • Two 80C86 Upward Compatible Operating Modes - 80C286 Real Address Mode - PVAM • Compatible with 80287 Numeric Data Co-Processor • High Bandwidth Bus Interface (25 Megabyte/Sec) • Available In - 68 Pin PGA (Commercial, Industrial, and Military) - 68 Pin PLCC (Commercial and Industrial) The Intersil 80C286 is a static CMOS version of the NMOS 80286 microprocessor. The 80C286 is an advanced, highperformance microprocessor with specially optimized capabilities for multiple user and multi-tasking systems. The 80C286 has built-in memory protection that supports operating system and task isolation as well as program and data privacy within tasks. A 25MHz 80C286 provides up to nineteen times the throughput of a standard 5MHz 8086. The 80C286 includes memory management capabilities that map 230 (one gigabyte) of virtual address space per task into 224 bytes (16 megabytes) of physical memory. The 80C286 is upwardly compatible with 80C86 and 80C88 software (the 80C286 instruction set is a superset of the 80C86/80C88 instruction set). Using the 80C286 real address mode, the 80C286 is object code compatible with existing 80C86 and 80C88 software. In protected virtual address mode, the 80C286 is source code compatible with 80C86 and 80C88 software but may require upgrading to use virtual address as supported by the 80C286’s integrated memory management and protection mechanism. Both modes operate at full 80C286 performance and execute a superset of the 80C86 and 80C88 instructions. The 80C286 provides special operations to support the efficient implementation and execution of operating systems. For example, one instruction can end execution of one task, save its state, switch to a new task, load its state, and start execution of the new task. The 80C286 also supports virtual memory systems by providing a segment-not-present exception and restartable instructions. Ordering Information PACKAGE PGA PLCC TEMP. RANGE 10MHz 0oC to +70oC - 12.5MHz CG80C286-12 16MHz CG80C286-16 -40oC to +85oC IG80C286-10 IG80C286-12 - -55oC to +125oC 59629067801MXC 59629067802MXC - 0oC to +70oC -40oC to +85oC FN2947 Rev.3.00 January 28, 2008 IS80C286-10 20MHz CG80C286-20 25MHz PKG. NO. - G68.B - - G68.B - - G68.B CS80C286-12 CS80C286-16 CS80C286-20 IS80C286-12 IS80C286-16 IS80C286-20 CS80C286-25 - N68.95 N68.95 Page 1 of 65 80C286 Pinouts D12 D13 D14 D4 D5 D6 D7 ERROR 43 45 47 49 51 38 40 42 44 46 48 50 53 52 ERROR NC A2 A1 32 33 55 54 NC BUSY VCC CLK 30 31 57 56 INTR NC A3 RESET 28 29 59 58 NMI NC A5 A4 26 27 61 60 PEREQ VSS A7 A6 24 25 63 62 READY VCC A9 A8 22 23 65 64 HLDA HOLD A11 A10 20 21 67 66 M/IO COD/INTA A13 A12 18 19 16 14 12 10 8 6 4 2 68 NC LOCK 17 15 13 11 9 7 5 3 1 A12 A15 A17 A19 A21 A22 PEACK S1 NC A16 A18 A20 VSS A23 S0 D15 D11 D3 41 36 PIN 1 INDICATOR BHE NC D10 D2 39 34 D9 D1 37 D0 D8 D0 35 A0 A14 VSS 68 LEAD PGA Component Pad View - As viewed from underside of the component when mounted on the board. D14 D13 D12 D11 D10 D9 D8 VSS D7 D6 D5 D4 D3 D2 D1 D0 51 49 47 45 43 41 39 37 35 50 48 46 44 42 40 38 36 34 D0 A0 33 32 A1 A2 VCC ERROR 52 53 BUSY NC 54 55 NC INTR 56 57 31 30 CLK NC NMI 58 59 29 28 RESET A3 VSS PEREQ 60 61 27 26 A4 A5 VCC READY 62 63 25 24 A6 A7 14 16 19 18 A12 A13 1 3 5 7 9 11 13 15 17 A12 12 A14 10 A15 8 A16 6 A17 4 A18 2 A19 68 A20 NC A21 LOCK VSS A11 A22 A9 A10 A23 A8 20 PEACK 22 21 S0 23 67 S1 65 66 NC 64 M/IO NC HLDA BHE HOLD COD/INTA PIN 1 INDICATOR FN2947 Rev.3.00 January 28, 2008 D15 NC ERROR 68 LEAD PGA P.C. Board View - As viewed from the component side of the P.C. board. Page 2 of 65 80C286 Pinouts (Continued) LOCK M/IO COD/INTA HLDA HOLD READY VCC PEREQ VSS NMI NC INTR NC NC BUSY ERROR NC 68 LEAD PLCC P.C. Board View - As viewed from the component side of the P.C. board. PIN 1 INDICATOR MOLD MARK DOES NOT INDICATE PIN 1 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 BHE NC NC S1 S0 PEACK A23 A22 VSS A21 A20 A19 A18 A17 A16 A15 A14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 D15 D7 D14 D6 D13 D5 D12 D4 D11 D3 D10 D2 D9 D1 D8 D0 VSS A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 RESET VCC CLK A2 A1 A0 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Functional Diagram ADDRESS UNIT (AU) ADDRESS LATCHES AND DRIVERS SEGMENT BASES OFFSET ADDER SEGMENT LIMIT SEGMENT CHECKER SIZES PHYSICAL ADDRESS ADDER PREFETCHER BUS CONTROL DATA TRANSCEIVERS 6-BYTE PREFETCH QUEUE ALU REGISTERS CONTROL PROCESSOR EXTENSION INTERFACE A23 - A0, BHE, M/IO PEACK PEREQ READY, HOLD, S1, S0, COD/INTA, LOCK, HLDA D15 - D0 BUS UNIT (BU) RESET 3 DECODED INSTRUCTION INSTRUCTION DECODER QUEUE INSTRUCTION UNIT (IU) CLK VSS VCC EXECUTION UNIT (EU) NMI BUSY INTR ERROR FN2947 Rev.3.00 January 28, 2008 Page 3 of 65 80C286 Pin Descriptions The following pin function descriptions are for the 80C286 microprocessor. SYMBOL PIN NUMBER TYPE DESCRIPTION CLK 31 I SYSTEM CLOCK: provides the fundamental timing for the 80C286 system. It is divided by two inside the 80C286 to generate the processor clock. The internal divide-by-two circuitry can be synchronized to an external clock generator by a LOW to HIGH transition on the RESET input. D15 - D0 36 - 51 I/O DATA BUS: inputs data during memory, I/O, and interrupt acknowledge read cycles; outputs data during memory and I/O write cycles. The data bus is active HIGH and is held at high impedance to the last valid logic level during bus hold acknowledge. A23 - A0 7-8 10 - 28 32 - 43 O ADDRESS BUS: outputs physical memory and I/O port addresses. A23 - A16 are LOW during I/O transfers. A0 is LOW when data is to be transferred on pins D7 - D0 (see table below). The address bus is active High and floats to three-state off during bus hold acknowledge. BHE 1 O BUS HIGH ENABLE: indicates transfer of data on the upper byte of the data bus, D15 - D8. Eight-bit oriented devices assigned to the upper byte of the data bus would normally use BHE to condition chip select functions. BHE is active LOW and floats to three-state OFF during bus hold acknowledge. BHE AND A0 ENCODINGS S1, S0 4, 5 O BHE VALUE A0 VALUE 0 0 Word transfer 0 1 Byte transfer on upper half of data bus (D15 - D8) 1 0 Byte transfer on lower half of data bus (D7 - D0) 1 1 Reserved FUNCTION BUS CYCLE STATUS: indicates initiation of a bus cycle and along with M/IO and COD/lNTA, defines the type of bus cycle. The bus is in a TS state whenever one or both are LOW. S1 and S0 are active LOW and are held at a high impedance logic one during bus hold acknowledge. 80C286 BUS CYCLE STATUS DEFINITION FN2947 Rev.3.00 January 28, 2008 COD/INTA M/IO S1 S0 0(LOW) 0 0 0 Interrupt acknowledge 0 0 0 1 Reserved 0 0 1 0 Reserved 0 0 1 1 None; not a status cycle 0 1 0 0 If A1 = 1 then halt; else shutdown 0 1 0 1 Memory data read 0 1 1 0 Memory data write 0 1 1 1 None; not a status cycle 1(HIGH) 0 0 0 Reserved 1 0 0 1 I/O read 1 0 1 0 I/O write 1 0 1 1 None; not a status cycle 1 1 0 0 Reserved 1 1 0 1 Memory instruction read 1 1 1 0 Reserved 1 1 1 1 None; not a status cycle BUS CYCLE INITIATED Page 4 of 65 80C286 Pin Descriptions The following pin function descriptions are for the 80C286 microprocessor. (Continued) SYMBOL PIN NUMBER TYPE DESCRIPTION M/IO 67 O MEMORY I/O SELECT: distinguishes memory access from I/O access. If HIGH during TS, a memory cycle or a halt/shutdown cycle is in progress. If LOW, an I/O cycle or an interrupt acknowledge cycle is in progress. M/IO is held at high impedance to the last valid logic state during bus hold acknowledge. COD/lNTA 66 O CODE/INTERRUPT ACKNOWLEDGE: distinguishes instruction fetch cycles from memory data read cycles. Also distinguishes interrupt acknowledge cycles from I/O cycles. COD/lNTA is held at high impedance to the last valid logic state during bus hold acknowledge. Its timing is the same as M/IO. LOCK 68 O BUS LOCK: indicates that other system bus masters are not to gain control of the system bus for the current and following bus cycles. The LOCK signal may be activated explicitly by the “LOCK” instruction prefix or automatically by 80C286 hardware during memory XCHG instructions, interrupt acknowledge, or descriptor table access. LOCK is active LOW and is held at a high impedance logic one during bus hold acknowledge. READY 63 l BUS READY: terminates a bus cycle. Bus cycles are extended without limit until terminated by READY LOW. READY is an active LOW synchronous input requiring setup and hold times relative to the system clock be met for correct operation. READY is ignored during bus hold acknowledge. (See Note 1) HOLD HLDA 64 65 I O BUS HOLD REQUEST AND HOLD ACKNOWLEDGE: control ownership of the 80C286 local bus. The HOLD input allows another local bus master to request control of the local bus. When control is granted, the 80C286 will float its bus drivers and then activate HLDA, thus entering the bus hold acknowledge condition. The local bus will remain granted to the requesting master until HOLD becomes inactive which results in the 80C286 deactivating HLDA and regaining control of the local bus. This terminates the bus hold acknowledge condition. HOLD may be asynchronous to the system clock. These signals are active HIGH. Note that HLDA never floats. INTR 57 I INTERRUPT REQUEST: requires the 80C286 to suspend its current program execution and service a pending external request. Interrupt requests are masked whenever the interrupt enable bit in the flag word is cleared. When the 80C286 responds to an interrupt request, it performs two interrupt acknowledge bus cycles to read an 8-bit interrupt vector that identifies the source of the interrupt. To ensure program interruption, INTR must remain active until an interrupt acknowledge bus cycle is initiated. INTR is sampled at the beginning of each processor cycle and must be active HIGH at least two processor cycles before the current instruction ends in order to interrupt before the next instruction. INTR is level sensitive, active HIGH, and may be asynchronous to the system clock. NMI 59 l NON-MASKABLE INTERRUPT REQUEST: interrupts the 80C286 with an internally supplied vector value of two. No interrupt acknowledge cycles are performed. The interrupt enable bit in the 80C286 flag word does not affect this input. The NMI input is active HIGH, may be asynchronous to the system clock, and is edge triggered after internal synchronization. For proper recognition, the input must have been previously LOW for at least four system clock cycles and remain HIGH for at least four system clock cycles. PEREQ PEACK 61 6 l O PROCESSOR EXTENSION OPERAND REQUEST AND ACKNOWLEDGE: extend the memory management and protection capabilities of the 80C286 to processor extensions. The PEREQ input requests the 80C286 to perform a data operand transfer for a processor extension. The PEACK output signals the processor extension when the requested operand is being transferred. PEREQ is active HIGH. PEACK is active LOW and is held at a high impedance logic one during bus hold acknowledge. PEREQ may be asynchronous to the system clock. BUSY ERROR 54 53 l I PROCESSOR EXTENSION BUSY AND ERROR: indicates the operating condition of a processor extension to the 80C286. An active BUSY input stops 80C286 program execution on WAIT and some ESC instructions until BUSY becomes inactive (HIGH). The 80C286 may be interrupted while waiting for BUSY to become inactive. An active ERROR input causes the 80C286 to perform a processor extension interrupt when executing WAIT or some ESC instructions. These inputs are active LOW and may be asynchronous to the system clock. FN2947 Rev.3.00 January 28, 2008 Page 5 of 65 80C286 Pin Descriptions The following pin function descriptions are for the 80C286 microprocessor. (Continued) SYMBOL PIN NUMBER TYPE DESCRIPTION RESET 29 l SYSTEM RESET: clears the internal logic of the 80C286 and is active HIGH. The 80C286 may be reinitialize at any time with a LOW to HIGH transition on RESET which remains active for more than 16 system clock cycles. During RESET active, the output pins of the 80C286 enter the state shown below. 80C286 PIN STATE DURING RESET PIN VALUE PIN NAMES 1 (HIGH) S0, S1, PEACK, A23 - A0, BHE, LOCK 0 (LOW) M/IO, COD/lNTA, HLDA (Note 2) HIGH IMPEDANCE D15 - D0 Operation of the 80C286 begins after a HlGH to LOW transition on RESET. The HIGH to LOW transition of RESET must be synchronous to the system clock. Approximately 50 system clock cycles are required by the 80C286 for internal initializations before the first bus cycle to fetch code from the power-on execution address is performed. A LOW to HIGH transition of RESET synchronous to the system clock will end a processor cycle at the second HIGH to LOW transition of the system clock. The LOW to HIGH transition of RESET may be asynchronous to the system clock; however, in this case it cannot be predetermined which phase of the processor clock will occur during the next system clock period. Synchronous LOW to HIGH transitions of RESET are required only for systems where the processor clock must be phase synchronous to another clock. VSS 9, 35, 60 l SYSTEM GROUND: are the ground pins (all must be connected to system ground). VCC 30, 62 l SYSTEM POWER: +5V power supply pins. A 0.1F capacitor between pins 60 and 62 is recommended. NOTES: 1. READY is an open-collector signal and should be pulled inactive with an appropriate resistor (620 at 10MHz and 12.5MHz, 470 at 16MHz, 390 at 20MHz, 270 at 25MHz). 2. HLDA is only Low if HOLD is inactive (Low). 3. All unused inputs should be pulled to their inactive state with pull up/down resistors. Functional Description Introduction The Intersil 80C286 microprocessor is a static CMOS version of the NMOS 80286 microprocessor. The 80C286 is an advanced, high-performance microprocessor with specially optimized capabilities for multiple user and multi-tasking systems. Depending on the application, the 80C286's performance is up to nineteen times faster than the standard 5MHz 8086's, while providing complete upward software compatibility with Intersil 80C86 and 80C88 CPU family. The 80C286 operates in two modes: 80C286 real address mode and protected virtual address mode. Both modes execute a superset of the 80C86 and 80C88 instruction set. In 80C286 real address mode programs use real addresses with up to one megabyte of address space. Programs use virtual addresses in protected virtual address mode, also called protected mode. In protected mode, the 80C286 CPU automatically maps 1 gigabyte of virtual addresses per task into a 16 megabyte real address space. This mode also provides memory protection to isolate the operating system and ensure privacy of each tasks' programs and data. Both modes provide the same base instruction set, registers and addressing modes. FN2947 Rev.3.00 January 28, 2008 The Functional Description describes the following: Static operation, the base 80C286 architecture common to both modes, 80C286 real address mode, and finally, protected mode. Static Operation The 80C286 is comprised of completely static circuitry. Internal registers, counters, and latches are static and require no refresh as with dynamic circuit design. This eliminates the minimum operating frequency restriction typically placed on microprocessors. The CMOS 80C286 can operate from DC to the specified upper frequency limit. The clock to the processor may be stopped at any point (either phase one or phase two of the processor clock cycle) and held there indefinitely. There is, however, a significant decrease in power requirement if the clock is stopped in phase two of the processor clock cycle. Details on the clock relationships will be discussed in the Bus Operation section. The ability to stop the clock to the processor is especially useful for system debug or power critical applications. Page 6 of 65 80C286 The 80C286 can be single-stepped using only the CPU clock. This state can be maintained as long as necessary. Single step clock information allows simple interface circuitry to provide critical information for system debug. Static design also allows very low frequency operation (down to DC). In a power critical situation, this can provide low power operation since 80C286 power dissipation is directly related to operating frequency. As the system frequency is reduced, so is the operating power until, ultimately, with the clock stopped in phase two of the processor clock cycle, the 80C286 power requirement is the standby current (5mA maximum). 16-BIT REGISTER NAME 7 BYTE ADDRESSABLE (8-BIT REGISTER NAMES SHOWN) SPECIAL REGISTER FUNCTIONS 07 AX AH AL DX DH DL CX CH CL BX BH BL The 80C86, 80C88, and 80C286 CPU family all contain the same basic set of registers, instructions, and addressing modes. The 80C286 processor is upwardly compatible with the 80C86 and 80C88 CPU's. DI INDEX REGISTERS STACK POINTER SP 15 Register Set SEGMENT REGISTERS: Four 16-bit special purpose registers select, at any given time, the segments of memory that are immediately addressable for code, stack and data. (For usage, refer to Memory Organization.) BASE AND INDEX REGISTERS: Four of the general purpose registers may also be used to determine offset addresses of operands in memory. These registers may contain base addresses or indexes to particular locations within a segment. The addressing mode determines the specific registers used for operand address calculations. STATUS AND CONTROL REGISTERS: Three 16-bit special purpose registers record or control certain aspects of the 80C286 processor state. These include the Flags register and Machine Status Word register shown in Figure 2, and the Instruction Pointer, which contains the offset address of the next sequential instruction to be executed. FN2947 Rev.3.00 January 28, 2008 LOOP/SHIFT/REPEAT COUNT BASE REGISTERS SI GENERAL REGISTERS: Eight 16-bit general purpose registers used to contain arithmetic and logical operands. Four of these (AX, BX, CX and DX) can be used either in their entirety as 16-bit words or split into pairs of separate 8-bit registers. MULTIPLY/DIVIDE I/O INSTRUCTIONS BP 80C286 Base Architecture The 80C286 base architecture has fifteen registers as shown in Figure 1. These registers are grouped into the following four categories. 0 GENERAL REGISTERS 15 0 0 CS CODE SEGMENT SELECTOR DS DATA SEGMENT SELECTOR SS STACK SEGMENT SELECTOR ES EXTRA SEGMENT SELECTOR SEGMENT REGISTERS 15 0 F IP MSW FLAGS INSTRUCTION POINTER MACHINE STATUS WORD STATUS AND CONTROL REGISTERS FIGURE 1. REGISTER SET Flags Word Description The Flags word (Flags) records specific characteristics of the result of logical and arithmetic instructions (bits 0, 2, 4, 6, 7 and 11) and controls the operation of the 80C286 within a given operating mode (bits 8 and 9). Flags is a 16-bit register. The function of the flag bits is given in Table 1. Page 7 of 65 80C286 STATUS FLAGS: CARRY PARITY AUXILIARY CARRY ZERO SIGN OVERFLOW 15 FLAGS: 14 13 NT 12 IOPL 11 OF 10 9 8 DF IF TF 7 SF 6 5 ZF 4 3 AF 2 1 PF 0 CF CONTROL FLAGS: TRAP FLAG INTERRUPT ENABLE DIRECTION FLAG SPECIAL FIELDS: I/O PRIVILEGE LEVEL NESTED TASK FLAG 15 MSW: RESERVED 3 2 1 0 TS EM MP PE TASK SWITCH PROCESSOR EXTENSION EMULATED MONITOR PROCESSOR EXTENSION PROTECTION ENABLE FIGURE 2. STATUS AND CONTROL REGISTER BIT FUNCTIONS TABLE 1. FLAGS WORD BIT FUNCTIONS BIT POSITION NAME 0 CF Carry Flag - Set on high-order bit carry or borrow; cleared otherwise. 2 PF Parity Flag - Set if low-order 8 bits of result contain an even number of 1 bits; cleared otherwise. 4 AF Set on carry from or borrow to the low order four bits of AL; cleared otherwise. 6 ZF Zero Flag - Set if result is zero; cleared otherwise. 7 SF Sign Flag - Set equal to high-order bit of result (0 if positive, 1 if negative). 11 OF Overflow Flag - Set if result is a too-large positive number or a too-small negative number (excluding sign-bit) to fit in destination operand; cleared otherwise. 8 TF Single Step Flag - Once set, a single step interrupt occurs after the next instruction executes. TF is cleared by the single step interrupt. 9 IF Interrupt-Enable Flag - When set, maskable interrupts will cause the CPU to transfer control to an interrupt vector specified location. 10 DF Direction Flag - Causes string instructions to auto decrement the appropriate index registers when set. Clearing DF causes auto increment. FN2947 Rev.3.00 January 28, 2008 FUNCTION Page 8 of 65 80C286 Instruction Set TABLE 2B. ARITHMETIC INSTRUCTIONS The instruction set is divided into seven categories: data transfer, arithmetic, string manipulation, shift/rotate/logical, high level, processor control and control transfer instructions. These categories are summarized in Table 2. An 80C286 instruction can reference zero, one, or two operands; where an operand may reside in a register, in the instruction itself, or in memory. Zero-operand instructions (e.g. NOP and HLT) are usually one byte long. One-operand instructions (e.g. INC and DEC) are usually two bytes long but some are encoded in only one byte. One-operand instructions may reference a register or memory location. Two-operand instructions permit the following six types of instruction operations: • Register to Register • Memory to Register • Immediate to Register • Memory to Memory • Register to Memory • Immediate to Memory Two-operand instructions (e.g. MOV and ADD) are usually three to six bytes long. Memory to memory operations are provided by a special class of string instructions requiring one to three bytes. For detailed instruction formats and encodings refer to the instruction set summary at the end of this document. TABLE 2A. DATA TRANSFER INSTRUCTIONS GENERAL PURPOSE ADDITION ADD Add byte or word ADC Add byte or word with carry INC Increment byte or word by 1 AAA ASClI adjust for addition DAA Decimal adjust for addition SUBTRACTION SUB Subtract byte or word SBB Subtract byte or word with borrow DEC Decrement byte or word by 1 NEG Negate byte or word CMP Compare byte or word AAS ASClI adjust for subtraction DAS Decimal adjust for subtraction MULTIPLICATION MUL Multiply byte or word unsigned lMUL Integer multiply byte or word AAM ASClI adjust for multiply DIVISION MOV Move byte or word DlV Divide byte or word unsigned PUSH Push word onto stack lDlV Integer divide byte or word Pop word off stack AAD ASClI adjust for division PUSHA Push all registers on stack CBW Convert byte to word POPA Pop all registers from stack CWD Convert word to doubleword XCHG Exchange byte or word XLAT Translate byte POP TABLE 2C. STRING INSTRUCTIONS INPUT/OUTPUT IN OUT Input byte or word Output byte or word ADDRESS OBJECT LEA Load effective address LDS Load pointer using DS LES Load pointer using ES FLAG TRANSFER LAHF Load AH register from flags SAHF Store AH register in flags PUSHF POPF Push flags onto stack MOVS Move byte or word string INS Input bytes or word string OUTS Output bytes or word string CMPS Compare byte or word string SCAS Scan byte or word string LODS Load byte or word string STOS Store byte or word string REP REPE/REPZ REPNE/REPNZ Repeat Repeat while equal/zero Repeat while not equal/not zero Pop flags off stack FN2947 Rev.3.00 January 28, 2008 Page 9 of 65 80C286 TABLE 2D. SHIFT/ROTATE LOGICAL INSTRUCTIONS TABLE 2F. PROCESSOR CONTROL INSTRUCTIONS FLAG OPERATIONS LOGICALS NOT “Not” byte or word STC Set carry flag AND “And” byte or word CLC Clear carry flag OR “Inclusive or” byte or word CMC Complement carry flag XOR “Exclusive or” byte or word STD Set direction flag TEST “Test” byte or word CLD Clear direction flag STl Set interrupt enable flag CLl Clear interrupt enable flag SHIFTS SHL/SAL Shift logical/arithmetic left byte or word SHR Shift logical right byte or word SAR Shift arithmetic right byte or word ROTATES ROL Rotate left byte or word ROR Rotate right byte or word RCL Rotate through carry left byte or word RCR Rotate through carry right byte or word EXTERNAL SYNCHRONIZATION HLT Halt until interrupt or reset WAIT Wait for TEST pin active ESC Escape to extension processor LOCK Lock bus during next instruction NO OPERATION NOP No operation EXECUTION ENVIRONMENT CONTROL TABLE 2E. HIGH LEVEL INSTRUCTIONS ENTER Format stack for procedure entry LEAVE Restore stack for procedure exit BOUND Detects values outside prescribed range LMSW Load machine status word SMSW Store machine status word TABLE 2G. PROGRAM TRANSFER INSTRUCTIONS CONDITIONAL TRANSFERS UNCONDITIONAL TRANSFERS JA/JNBE Jump if above/not below nor equal CALL Call procedure JAE/JNB Jump if above or equal/not below RET Return from procedure JB/JNAE Jump if below/not above nor equal JMP Jump JBE/JNA Jump if below or equal/not above JC JE/JZ Jump if carry Jump if equal/zero ITERATION CONTROLS LOOP JG/JNLE Jump if greater/not less nor equal JGE/JNL Jump if greater or equal/not less LOOPE/LOOPZ JL/JNGE Jump if less/not greater nor equal LOOPNE/LOOPNZ JLE/JNG Jump if less or equal/not greater JCXZ JNC JNE/JNZ JNO JNP/JPO Loop Loop if equal/zero Loop if not equal/not zero Jump if register CX = 0 Jump if not carry Jump if not equal/not zero Jump if not overflow INTERRUPTS INT Interrupt Jump if not parity/parity odd JNS Jump if not sign INTO Interrupt if overflow JO Jump if overflow lRET Interrupt return JP/JPE JS FN2947 Rev.3.00 January 28, 2008 Jump if parity/parity even Jump if sign Page 10 of 65 80C286 Memory Organization Addressing Modes Memory is organized as sets of variable-length segments. Each segment is a linear contiguous sequence of up to 64K (216) 8-bit bytes. Memory is addressed using a two-component address (a pointer) that consists of a 16-bit segment selector and a 16-bit offset. The segment selector indicates the desired segment in memory. The offset component indicates the desired byte address within the segment. (See Figure 3). The 80C286 provides a total of eight addressing modes for instructions to specify operands. Two addressing modes are provided for instructions that operate on register or immediate operands: All instructions that address operands in memory must specify the segment and the offset. For speed and compact instruction encoding, segment selectors are usually stored in the high speed segment registers. An instruction need specify only the desired segment register and offset in order to address a memory operand. POINTER SEGMENT 31 OFFSET 16 15 0 OPERAND SELECTED SELECTED SEGMENT REGISTER OPERAND MODE: The operand is located in one of the 8 or 16-bit general registers. IMMEDIATE OPERAND MODE: The operand is included in the instruction. Six modes are provided to specify the location of an operand in a memory segment. A memory operand address consists of two 16-bit components: segment selector and offset. The segment selector is supplied by a segment register either implicitly chosen by the addressing mode or explicitly chosen by a segment override prefix. The offset is calculated by summing any combination of the following three address elements: the displacement (an 8 or 16-bit immediate value contained in the instruction) the base (contents of either the BX or BP base registers) the index (contents of either the SI or Dl index registers) MEMORY FIGURE 3. TWO COMPONENT ADDRESS Most instructions need not explicitly specify which segment register is used. The correct segment register is automatically chosen according to the rules of Table 3. These rules follow the way programs are written (see Figure 4) as independent modules that require areas for code and data, a stack, and access to external data areas. Special segment override instruction prefixes allow the implicit segment register selection rules to be overridden for special cases. The stack, data and extra segments may coincide for simple programs. To access operands not residing in one of the four immediately available segments, a full 32-bit pointer or a new segment selector must be loaded. MODULE A CODE DATA MODULE B CODE CPU DATA CODE DATA STACK PROCESS STACK EXTRA SEGMENT REGISTERS TABLE 3. SEGMENT REGISTER SELECTION RULES MEMORY REFERENCE NEEDED SEGMENT REGISTER USED IMPLICIT SEGMENT SELECTION RULE Instructions Code (CS) Automatic with instruction prefetch Stack Stack (SS) All stack pushes and pops. Any memory reference which uses BP as a base register. Local Data Data (DS) All data references except when relative to stack or string destination External (Global) Data Extra (ES) Alternate data segment and destination of string operation FN2947 Rev.3.00 January 28, 2008 PROCESS DATA BLOCK 1 PROCESS DATA BLOCK 2 MEMORY FIGURE 4. SEGMENTED MEMORY HELPS STRUCTURE SOFTWARE Any carry out from the 16-bit addition is ignored. Eight-bit displacements are sign extended to 16-bit values. Page 11 of 65 80C286 Combinations of these three address elements define the six memory addressing modes, described below. DIRECT MODE: The operand's offset is contained in the instruction as an 8 or 16-bit displacement element. REGISTER INDIRECT MODE: The operand's offset is in one of the registers SI, Dl, BX or BP. BASED MODE: The operand's offset is the sum of an 8 or 16bit displacement and the contents of a base register (BX or BP). INDEXED MODE: The operand's offset is the sum of an 8 or 16-bit displacement and the contents of an index register (SI or Dl). BASED INDEXED MODE: The operand's offset is the sum of the contents of a base register and an index register. BASED INDEXED MODE WITH DISPLACEMENT: The operand's offset is the sum of a base register's contents, an index register's contents, and an 8 or 16-bit displacement. Data Types The 80C286 directly supports the following data types: Integer: Ordinal: Pointer: String: ASClI: A signed binary numeric value contained in an 8-bit byte or a 16-bit word. All operations assume a 2's complement representation. Signed 32 and 64-bit integers are supported using the 80287 Numeric Data Processor. An unsigned binary numeric value contained in an 8-bit byte or 16-bit word. A 32-bit quantity, composed of a segment selector component and an offset component. Each component is a 16-bit word. A contiguous sequence of bytes or words. A string may contain from 1 byte to 64K bytes. 7 SIGN BIT MAGNITUDE 7 A byte (unpacked) representation of the decimal digits 0-9. Packed BCD: A byte (packed) representation of two decimal digits 0-9 storing one digit in each nibble of the byte. Floating Point: A signed 32, 64 or 80-bit real number representation. (Floating point operands are supported using the 80287 Numeric Processor extension). Figure 5 graphically represents the data types supported by the 80C286. 0 UNSIGNED BYTE MSB MAGNITUDE 15 14 +1 0 8 7 0 SIGNED WORD SIGN BIT MSB SIGNED 31 DOUBLE WORD (NOTE) SIGN BIT +3 MAGNITUDE +2 16 15 +1 0 0 MSB MAGNITUDE SIGNED 63 QUAD WORD (NOTE) SIGN BIT +7 +6 +5 48 47 +4 +3 32 31 +2 +1 16 15 0 0 MSB MAGNITUDE 15 +1 0 0 UNSIGNED WORD MSB MAGNITUDE BINARY 7 CODED DECIMAL (BCD) +N 0 7 +1 07 0 0  BCD DIGIT N 7 +N BCD DIGIT 1 7 0 +1 BCD DIGIT 0 07 0 0  ASCII A byte representation of alphanumeric and control characters using the ASClI standard of character representation. BCD: 0 SIGNED BYTE ASCII CHARACTER1 ASCII CHARACTERN 7 +N 7 0 PACKED BCD +1 ASCII CHARACTER0 07 0 0  MOST SIGNIFICANT DIGIT 7/15 +N 0 7/15 LEAST SIGNIFICANT DIGIT +1 0 7/15 0 0  STRING BYTE/WORD N BYTE/WORD 1 31 +3 BYTE/WORD 0 +1 16 15 +1 0 0 POINTER OFFSET SELECTOR 79 +9 +8 +7 +6 +5 +4 +3 +2 +1 0 0 FLOATING POINT (NOTE) SIGN BIT EXPONENT MAGNITUDE FIGURE 5. 80C286 SUPPORTED DATA TYPES NOTE: Supported by 80C286/80C287 Numeric Data Processor Configuration FN2947 Rev.3.00 January 28, 2008 Page 12 of 65 80C286 TABLE 4. INTERRUPT VECTOR ASSIGNMENTS FUNCTION INTERRUPT NUMBER RELATED INSTRUCTIONS DOES RETURN ADDRESS POINT TO INSTRUCTION CAUSING EXCEPTION? Divide Error Exception 0 DlV, lDlV Single Step Interrupt 1 All NMI Interrupt 2 INT 2 or NMI Pin Breakpoint Interrupt 3 INT 3 INTO Detected Overflow Exception 4 INTO No BOUND Range Exceeded Exception s BOUND Yes Invalid Opcode Exception 6 Any Undefined Opcode Yes Processor Extension Not Available Exception 7 ESC or WAIT Yes Reserved - Do Not Use Processor Extension Error Interrupt Yes 8 - 15 16 Reserved 17 - 31 User Defined 32 - 255 ESC or WAIT I/O Space Maskable Interrupt (INTR) The I/O space consists of 64K 8-bit ports, 32K 16-bit ports, or a combination of the two. I/O instructions address the I/O space with either an 8-bit port address, specified in the instruction, or a 16-bit port address in the DX register. 8-bit port addresses are zero extended such that A15-A8 are LOW. I/O port addresses 00F8(H) through 00FF(H) are reserved. The 80C286 provides a maskable hardware interrupt request pin, INTR. Software enables this input by setting the interrupt flag bit (IF) in the flag word. All 224 user-defined interrupt sources can share this input, yet they can retain separate interrupt handlers. An 8-bit vector read by the CPU during the interrupt acknowledge sequence (discussed in System Interface section) identifies the source of the interrupt. Interrupts An interrupt transfers execution to a new program location. The old program address (CS:lP) and machine state (Flags) are saved on the stack to allow resumption of the interrupted program. Interrupts fall into three classes: hardware initiated, INT instructions, and instruction exceptions. Hardware initiated interrupts occur in response to an external input and are classified as non-maskable or maskable. Programs may cause an interrupt with an INT instruction. Instruction exceptions occur when an unusual condition which prevents further instruction processing is detected while attempting to execute an instruction. The return address from an exception will always point to the instruction causing the exception and include any leading instruction prefixes. A table containing up to 256 pointers defines the proper interrupt service routine for each interrupt. Interrupts 0-31, some of which are used for instruction exceptions, are reserved. For each interrupt, an 8-bit vector must be supplied to the 80C286 which identifies the appropriate table entry. Exceptions supply the interrupt vector internally. INT instructions contain or imply the vector and allow access to all 256 interrupts. Maskable hardware initiated interrupts supply the 8-bit vector to the CPU during an interrupt acknowledge bus sequence. Nonmaskable hardware interrupts use a predefined internally supplied vector. FN2947 Rev.3.00 January 28, 2008 The processor automatically disables further maskable interrupts internally by resetting the IF as part of the response to an interrupt or exception. The saved flag word will reflect the enable status of the processor prior to the interrupt. Until the flag word is restored to the flag register, the interrupt flag will be zero unless specifically set. The interrupt return instruction includes restoring the flag word, thereby restoring the original status of IF. Non-Maskable Interrupt Request (NMI) A non-maskable interrupt input (NMI) is also provided. NMI has higher priority than INTR. A typical use of NMI would be to activate a power failure routine. The activation of this input causes an interrupt with an internally supplied vector value of 2. No external interrupt acknowledge sequence is performed. While executing the NMI servicing procedure, the 80C286 will service neither further NMI requests, INTR requests, nor the processor extension segment overrun interrupt until an interrupt return (lRET) instruction is executed or the CPU is reset. If NMI occurs while currently servicing an NMI, its presence will be saved for servicing after executing the first IRET instruction. IF is cleared at the beginning of an NMI interrupt to inhibit INTR interrupts. Page 13 of 65 80C286 Single Step Interrupt The 80C286 has an internal interrupt that allows programs to execute one instruction at a time. It is called the single step interrupt and is controlled by the single step flag bit (TF) in the flag word. Once this bit is set, an internal single step interrupt will occur after the next instruction has been executed. The interrupt clears the TF bit and uses an internally supplied vector of 1. The lRET instruction is used to set the TF bit and transfer control to the next instruction to be single stepped. takes place and controls the operating mode of the 80C286. It is a 16-bit register of which the lower four bits are used. One bit places the CPU into protected mode, while the other three bits, as shown in Table 7, control the processor extension interface. After RESET, this register contains FFF0(H) which places the 80C286 in 80C286 real address mode. TABLE 7. MSW BIT FUNCTIONS BIT POSITION NAME FUNCTION 0 PE Protected mode enable places the 80C286 into protected mode and cannot be cleared except by RESET. 1 MP Monitor processor extension allows WAIT instructions to cause a processor extension not present exception (number 7). 2 EM Emulate processor extension causes a processor extension not present exception (number 7) on ESC instructions to allow emulating a processor extension. 3 TS Task switched indicates the next instruction using a processor extension will cause exception 7, allowing software to test whether the current processor extension context belongs to the current task. Interrupt Priorities When simultaneous interrupt requests occur, they are processed in a fixed order as shown in Table 5. Interrupt processing involves saving the flags, return address, and setting CS:lP to point at the first instruction of the interrupt handler. If another enabled interrupt should occur, it is processed before the next instruction of the current interrupt handler is executed. The last interrupt processed is therefore the first one serviced. TABLE 5. INTERRUPT PROCESSING ORDER ORDER INTERRUPT 1 Instruction Exception 2 Single Step 3 NMI 4 Processor Extension Segment Overrun 5 INTR 6 INT Instruction The LMSW and SMSW instructions can load and store the MSW in real address mode. The recommended use of TS, EM, and MP is shown in Table 8. Halt Initialization and Processor Reset Processor initialization or start up is accomplished by driving the RESET input pin HIGH. RESET forces the 80C286 to terminate all execution and local bus activity. No instruction or bus activity will occur as long as RESET is active. After RESET becomes inactive, and an internal processing interval elapses, the 80C286 begins execution in real address mode with the instruction at physical location FFFFF0(H). RESET also sets some registers to predefined values as shown in Table 6. The HLT instruction stops program execution and prevents the CPU from using the local bus until restarted. Either NMI, INTR with IF = 1, or RESET will force the 80C286 out of halt. If interrupted, the saved CS:IP will point to the next instruction after the HLT. TABLE 6. 80C286 INITIAL REGISTER STATE AFTER RESET Flag Word 0002(H) Machine Status Word FFF0(H) Instruction Pointer FFF0(H) Code Segment F000(H) Data Segment 0000(H) Extra Segment 0000(H) Stack Segment 0000(H) HOLD must not be active during the time from the leading edge of the initial RESET to 34 CLKs after the trailing edge of the initial RESET of an 80C286 system. Machine Status Word Description The machine status word (MSW) records when a task switch FN2947 Rev.3.00 January 28, 2008 Page 14 of 65 80C286 TABLE 8. RECOMMENDED MSW ENCODINGS FOR PROCESSOR EXTENSION CONTROL TS MP EM RECOMMENDED USE INSTRUCTION CAUSING EXCEPTION 7 0 0 0 Initial encoding after RESET. 80C286 operation is identical to 80C86/88. None 0 0 1 No processor extension is available. Software will emulate its function. ESC 1 0 1 No processor extension is available. Software will emulate its function. The current processor extension context may belong to another task. ESC 0 1 0 A processor extension exists. None 1 1 0 A processor extension exists. The current processor extension context may belong to another task. The exception 7 on WAIT allows software to test for an error pending from a previous processor extension operation. ESC or WAIT TABLE 9. REAL ADDRESS MODE ADDRESSING INTERRUPTS FUNCTION INTERRUPT NUMBER RETURN ADDRESS BEFORE INSTRUCTION Interrupt table limit too small exception 8 INT vector is not within table limit Yes Processor extension segment overrun interrupt 9 ESC with memory operand extending beyond offset FFFF(H) No Segment overrun exception 13 Word memory reference with offset = FFFF(H) or an attempt to execute past the end of a segment Yes RELATED INSTRUCTIONS 80C286 Real Address Mode The 80C286 executes a fully upward-compatible superset of the 80C86 instruction set in real address mode. In real address mode the 80C286 is object code compatible with 80C86 and 80C88 software. The real address mode architecture (registers and addressing modes) is exactly as described in the 80C286 Base Architecture section of this Functional Description. the segment may be overlaid by another segment to reduce physical memory requirements. 15 0 0000 OFFSET ADDRESS OFFSET Memory Size Physical memory is a contiguous array of up to 1,048,576 bytes (one megabyte) addressed by pins A0 through A19 and BHE. A20 through A23 should be ignored. 15 0 SEGMENT SELECTOR SEGMENT ADDRESS 0000 Memory Addressing In real address mode physical memory is a contiguous array of up to 1,048,576 bytes (one megabyte) addressed by pin A0 through A19 and BHE. Address bits A20-A23 may not always be zero in real mode. A20-A23 should not be used by the system while the 80C286 is operating in Real Mode. The selector portion of a pointer is interpreted as the upper 16bits of a 20-bit segment address. The lower four bits of the 20bit segment address are always zero. Segment addresses, therefore, begin on multiples of 16 bytes. See Figure 6 for a graphic representation of address information. All segments in real address mode are 64K bytes in size and may be read, written, or executed. An exception or interrupt can occur if data operands or instructions attempt to wrap around the end of a segment (e.g. a word with its low order byte at offset FFFF(H) and its high order byte at offset 0000(H)). If, in real address mode, the information contained in a segment does not use the full 64K bytes, the unused end of FN2947 Rev.3.00 January 28, 2008 ADDER 19 0 20-BIT PHYSICAL MEMORY ADDRESS FIGURE 6. 80C286 REAL ADDRESS MODE ADDRESS CALCULATION Page 15 of 65 80C286 Reserved Memory Locations Protected Virtual Address Mode The 80C286 reserves two fixed areas of memory in real address mode (see Figure 7); system initialization area and interrupt table area. Locations from addresses FFFF0(H) through FFFFF(H) are reserved for system initialization. Initial execution begins at location FFFF0(H). Locations 00000(H) through 003FF(H) are reserved for interrupt vectors. The 80C286 executes a fully upward-compatible superset of the 80C86 instruction set in protected virtual address mode (protected mode). Protected mode also provides memory management and protection mechanisms and associated instructions. RESET BOOTSTRAP PROGRAM JUMP    INTERRUPT POINTER FOR VECTOR 255    INTERRUPT POINTER FOR VECTOR 1 INTERRUPT POINTER FOR VECTOR 0 FFFFFH FFFF0H 3FFH 3FCH 7H 4H 3H 0H The 80C286 enters protected virtual address mode from real address mode by setting the PE (Protection Enable) bit of the machine status word with the Load Machine Status Word (LMSW) instruction. Protected mode offers extended physical and virtual memory address space, memory protection mechanisms, and new operations to support operating systems and virtual memory. All registers, instructions, and addressing modes described in the 80C286 Base Architecture section of this Functional Description remain the same. Programs for the 80C86, 80C88, and real address mode 80C286 can be run in protected mode; however, embedded constants for segment selectors are different. Memory Size FIGURE 7. 80C286 REAL ADDRESS MODE INITIALLY RESERVED MEMORY LOCATIONS Interrupts Table 9 shows the interrupt vectors reserved for exceptions and interrupts which indicate an addressing error. The exceptions leave the CPU in the state existing before attempting to execute the failing instruction (except for PUSH, POP, PUSHA, or POPA). Refer to the next section on protected mode initialization for a discussion on exception 8. The protected mode 80C286 provides a 1 gigabyte virtual address space per task mapped into a 16 megabyte physical address space defined by the address pins A23-A0 and BHE. The virtual address space may be larger than the physical address space since any use of an address that does not map to a physical memory location will cause a restartable exception. CPU 31 16 15 0 POINTER SELECTOR OFFSET Protected Mode Initialization PHYSICAL MEMORY To prepare the 80C286 for protected mode, the LIDT instruction is used to load the 24-bit interrupt table base and 16-bit limit for the protected mode interrupt table. This instruction can also set a base and limit for the interrupt vector table in real address mode. After reset, the interrupt table base is initialized to 000000(H) and its size set to 03FF(H). These values are compatible with 80C86 and 80C88 software. LIDT should only be executed in preparation for protected mode. PHYSICAL ADDRESS ADDER MEMORY OPERAND Shutdown Shutdown occurs when a severe error is detected that prevents further instruction processing by the CPU. Shutdown and halt are externally signalled via a halt bus operation. They can be distinguished by A1 HIGH for halt and A1 LOW for shutdown. In real address mode, shutdown can occur under two conditions: • Exceptions 8 or 13 happen and the IDT limit does not include the interrupt vector. • A CALL INT or PUSH instruction attempts to wrap around the stack segment when SP is not even. An NMI input can bring the CPU out of shutdown if the IDT limit is at least 000F(H) and SP is greater than 0005(H), otherwise shutdown can only be exited via the RESET input. FN2947 Rev.3.00 January 28, 2008 SEGMENT BASE ADDRESS 23 SEGMENT DESCRIPTOR 0 SEGMENT SEGMENT DESCRIPTION TABLE INITIAL CS:IP VALUE IS F000:FFF0 FIGURE 8. PROTECTED MODE MEMORY ADDRESSING Memory Addressing As in real address mode, protected mode uses 32-bit pointers, consisting of 16-bit selector and offset components. The selector, however, specifies an index into a memory resident table rather than the upper 16-bits of a real memory address. The 24-bit base address of the desired segment is obtained from Page 16 of 65 80C286 the tables in memory. The 16-bit offset is added to the segment base address to form the physical address as shown in Figure 8. The tables are automatically referenced by the CPU whenever a segment register is loaded with a selector. All 80C286 instructions which load a segment register will reference the memory based tables without additional software. The memory based tables contain 8 byte values called descriptors. 7 0 7 +7 ACCESS RIGHTS BYTE +5 P DPL S TYPE A RESERVED † +6 BASE 23 - 16 +4 +3 BASE 15 - 0 +1 LIMIT 15 - 0 15 Descriptors 0 8 7 +2 0 0 † MUST BE SET TO 0 FOR COMPATIBILITY WITH FUTURE UPGRADES Descriptors define the use of memory. Special types of descriptors also define new functions for transfer of control and task switching. The 80C286 has segment descriptors for code, stack and data segments, and system control descriptors for special system data segments and control transfer operations. Descriptor accesses are performed as locked bus operations to assure descriptor integrity in multi-processor systems. Code and Data Segment Descriptors (S = 1) Besides segment base addresses, code and data descriptors contain other segment attributes including segment size (1 to 64K bytes), access rights (read only, read/write, execute only, and execute/read), and presence in memory (for virtual memory systems) (See Table 10). Any segment usage violating a segment attribute indicated by the segment descriptor will prevent the memory cycle and cause an exception or interrupt. FIGURE 9. CODE OR DATA SEGMENT DESCRIPTOR Code and data (including stack data) are stored in two types of segments: code segments and data segments. Both types are identified and defined by segment descriptors (S = 1). Code segments are identified by the executable (E) bit set to 1 in the descriptor access rights byte. The access rights byte of both code and data segment descriptor types have three fields in common: present (P) bit, Descriptor Privilege Level (DPL), and accessed (A) bit. If P = 0, any attempted use of this segment will cause a not-present exception. DPL specifies the privilege level of the segment descriptor. DPL controls when the descriptor may be used by a task (refer to privilege discussion below). The A bit shows whether the segment has been previously accessed for usage profiling, a necessity for virtual memory systems. The CPU will always set this bit when accessing the descriptor. TABLE 10. CODE AND DATA SEGMENT DESCRIPTOR FORMATS - ACCESS RIGHTS BYTE DEFINITION BIT POSITION 7 6-5 4 Present (P) FUNCTION P=1 Segment is mapped into physical memory. P=0 No mapping to physical memory exits, base and limit are not used. Descriptor Privilege Level (DPL) Segment privilege attribute used in privilege tests. Segment Descriptor (S) S = 1 Code or Data (includes stacks) segment descriptor S=0 System Segment Descriptor or Gate Descriptor 3 Executable (E) E=0 Data segment descriptor type is: 2 Expansion Direction (ED) ED = 0 Expand up segment, offsets must be  limit. ED = 1 Expand down segment, offsets must be > limit. Writable (W) W=0 Data segment may not be written into. W=1 Data segment may be written into. 1 Type Field Definition NAME If Data Segment (S = 1, E = 0) 3 Executable (E) E=1 Code Segment Descriptor type is: 2 Conforming (C) C=1 Code segment may only be executed when CPL  DPL and CPL remains unchanged. 1 Readable (R) R=0 Code segment may not be read. R=1 Code segment may be read. A=0 Segment has not been accessed. A=1 Segment selector has been loaded into segment register or used by selector test instructions. 0 FN2947 Rev.3.00 January 28, 2008 Accessed (A) If Code Segment (S = 1, E = 1) Page 17 of 65 80C286 Data segments (S = 1, E = 0) may be either read-only or readwrite as controlled by the W bit of the access rights byte. Readonly (W = 0) data segments may not be written into. Data segments may grow in two directions, as determined by the Expansion Direction (ED) bit: upwards (ED = 0) for data segments, and downwards (ED = 1) for a segment containing a stack. The limit field for a data segment descriptor is interpreted differently depending on the ED bit (see Table 10). A code segment (S = 1, E = 1) may be execute-only or execute/read as determined by the Readable (R) bit. Code segments may never be written into and execute-only code segments (R = 0) may not be read. A code segment may also have an attribute called conforming (C). A conforming code segment may be shared by programs that execute at different privilege levels. The DPL of a conforming code segment defines the range of privilege levels at which the segment may be executed (refer to privilege discussion below). The limit field identifies the last byte of a code segment. TABLE 11. SYSTEM SEGMENT DESCRIPTOR FORMAT FIELDS NAME VALUE TYPE 1 Available Task State Segment (TSS) 2 Local Descriptor Table 3 Busy Task State Segment (TSS) 0 Descriptor contents are not valid 1 Descriptor contents are valid P DESCRIPTION DPL 0-3 Descriptor Privilege Level BASE 24-Bit Number Base Address of special system data segment in real memory LIMIT 16-Bit Number Offset of last byte in segment System Segment Descriptors (S = 0, Type = 1-3) Gate Descriptors (S = 0, Type = 4-7) In addition to code and data segment descriptors, the protected mode 80C286 defines System Segment Descriptors. These descriptors define special system data segments which contain a table of descriptors (Local Descriptor Table Descriptor) or segments which contain the execution state of a task (Task State Segment Descriptor). Gates are used to control access to entry points within the target code segment. The gate descriptors are call gates, task gates, interrupt gates and trap gates. Gates provide a level of indirection between the source and destination of the control transfer. This indirection allows the CPU to automatically perform protection checks and control entry point of the destination. Call gates are used to change privilege levels (see Privilege), task gates are used to perform a task switch, and interrupt and trap gates are used to specify interrupt service routines. The interrupt gate disables interrupts (resets IF) while the trap gate does not. Table 11 gives the formats for the special system data segment descriptors. The descriptors contain a 24-bit base address of the segment and a 16-bit limit. The access byte defines the type of descriptor, its state and privilege level. The descriptor contents are valid and the segment is in physical memory if P = 1. If P = 0, the segment is not valid. The DPL field is only used in Task State Segment descriptors and indicates the privilege level at which the descriptor may be used (see Privilege). Since the Local Descriptor Table descriptor may only be used by a special privileged instruction, the DPL field is not used. Bit 4 of the access byte is 0 to indicate that it is a system control descriptor. The type field specifies the descriptor type as indicated in Table 11. 7 +7 0 7 0 +6 RESERVED † +5 P DPL 0 BASE 23 - 16 TYPE +3 BASE 15 - 0 +1 LIMIT 15 - 0 15 8 7 +4 +2 0 0 † MUST BE SET TO 0 FOR COMPATIBILITY WITH FUTURE UPGRADES FIGURE 10. SYSTEM SEGMENT DESCRIPTOR FN2947 Rev.3.00 January 28, 2008 Table 12 shows the format of the gate descriptors. The descriptor contains a destination pointer that points to the descriptor of the target segment and the entry point offset. The destination selector in an interrupt gate, trap gate, and call gate must refer to a code segment descriptor. These gate descriptors contain the entry point to prevent a program from constructing and using an illegal entry point. Task gates may only refer to a task state segment. Since task gates invoke a task switch, the destination offset is not used in the task gate. Exception 13 is generated when the gate is used if a destination selector does not refer to the correct descriptor type. The word count field is used in the call gate descriptor to indicate the number of parameters (0-31 words) to be automatically copied from the caller’s stack to the stack of the called routine when a control transfer changes privilege levels. The word count field is not used by any other gate descriptor. The access byte format is the same for all descriptors. P = 1 indicates that the gate contents are valid. P = 0 indicates the contents are not valid and causes exception 11 if referenced. DPL is the descriptor privilege level and specifies when this descriptor may be used by a task (refer to privilege discussion below). Bit 4 must equal 0 to indicate a system control descriptor. The type field specifies the descriptor type as indicated in Table 12. Page 18 of 65 80C286 Segment Descriptor Cache Registers PROGRAM VISIBLE SEGMENT SELECTORS A segment descriptor cache register is assigned to each of the four segment registers (CS, SS, DS, ES). Segment descriptors are automatically loaded (cached) into a segment descriptor cache register (Figure 12) whenever the associated segment register is loaded with a selector. CS DS SS ES Only segment descriptors may be loaded into segment descriptor cache registers. Once loaded, all references to that segment of memory use the cached descriptor information instead of reaccessing the descriptor. The descriptor cache registers are not visible to programs. No instructions exist to store their contents. They only change when a segment register is loaded. 7 0 7 +3 +1 PROGRAM INVISIBLE ACCESS RIGHTS SEGMENT PHYSICAL BASE ADDRESS SEGMENT SIZE +6 X X X WORD COUNT +4 4-0 X X +2 DESTINATION SELECTOR 15 - 0 +5 P DPL 0 0 0 RESERVED † +7 15 SEGMENT REGISTERS (LOADED BY PROGRAM) TYPE 40 39 16 15 0 SEGMENT DESCRIPTOR CACHE REGISTERS (AUTOMATICALLY LOADED BY CPU) 0 DESTINATION OFFSET 15 - 0 8 7 47 0 15 † MUST BE SET TO 0 FOR COMPATIBILITY WITH FUTURE UPGRADES FIGURE 12. DESCRIPTOR CACHE REGISTERS FIGURE 11. GATE DESCRIPTOR SELECTOR INDEX TABLE 12. GATE DESCRIPTOR FORMAT FIELD NAME VALUE TYPE 4 Call Gate 5 Task Gate 6 Interrupt Gate 7 Trap Gate 0 Descriptor Contents are not valid 1 Descriptor Contents are valid P DESCRIPTION DPL 0-3 Descriptor Privilege Level WORD COUNT 0 - 31 Number of words to copy from callers stack to called procedures stack. Only used with call gate. DESTINATION 16-Bit Selector to the target code segment SELECTOR Selector (call, interrupt or selector Trap Gate). Selector to the target task state segment (Task Gate). DESTINATION OFFSET 16-Bit Offset Entry point within the target code segment Selector Fields A protected mode selector has three fields: descriptor entry index, local or global descriptor table indicator (TI), and selector privilege (RPL) as shown in Figure 13. These fields select one of two memory based tables of descriptors, select the appropriate table entry and allow high-speed testing of the selector's privilege attribute (refer to privilege discussion below). FN2947 Rev.3.00 January 28, 2008 15 BITS 1-0 2 15 - 3 8 NAME 7 TI RPL 2 1 0 FUNCTION Requested Privilege Level (RPL) Indicates Selector Privilege Level Desired Table Indicator (TI) TI = 0 Use Global Descriptor Table (GDT) TI = 1 Use Local Descriptor Table (LDT) Index Select Descriptor Entry In Table FIGURE 13. SELECTOR FIELDS Local and Global Descriptor Tables Two tables of descriptors, called descriptor tables, contain all descriptors accessible by a task at any given time. A descriptor table is a linear array of up to 8192 descriptors. The upper 13 bits of the selector value are an index into a descriptor table. Each table has a 24-bit base register to locate the descriptor table in physical memory and a 16-bit limit register that confine descriptor access to the defined limits of the table as shown in Figure 14. A restartable exception (13) will occur if an attempt is made to reference a descriptor outside the table limits. One table, called the Global Descriptor table (GDT), contains descriptors available to all tasks. The other table, called the Local Descriptor Table (LDT), contains descriptors that can be private to a task. Each task may have its own private LDT. The GDT may contain all descriptor types except interrupt and trap descriptors. The LDT may contain only segment, task gate, and call gate descriptors. A segment cannot be accessed by a task if its segment descriptor does not exist in either descriptor table at the time of access. Page 19 of 65 80C286 CPU MEMORY MEMORY GATE FOR INTERRUPT #n 0 GDT LIMIT 23 GDT GATE FOR INTERRUPT #n-1 GDT BASE 24-BIT PHYS AD 15 CPU 0 15 LDT DESCR SELECTOR 15 IDT LIMIT LDT1 CURRENT LDT LDT BASE 24-BIT PHYS AD 0 FIGURE 16. INTERRUPT DESCRIPTOR TABLE DEFINITION LDTn INCREASING MEMORY ADDRESS PROGRAM INVISIBLE (AUTOMATICALLY LOADED FROM LDT DESCR WITHIN GDT) FIGURE 14. LOCAL AND GLOBAL DESCRIPTOR TABLE DEFINITION The LGDT and LLDT instructions load the base and limit of the global and local descriptor tables. LGDT and LLDT are privileged, i.e. they may only be executed by trusted programs operating at level 0. The LGDT instruction loads a six byte field containing the 16-bit table limit and 24-bit physical base address of the Global Descriptor Table as shown in Figure 15. The LDT instruction loads a selector which refers to a Local Descriptor Table descriptor containing the base address and limit for an LDT, as shown in Table 11. 7 0 7 0 BASE 23 - 16 RESERVED † +5 23 +4 +3 BASE 15 - 0 +2 +1 LIMIT 15 - 0 0 15 8 7 Privilege The 80C286 has a four-level hierarchical privilege system which controls the use of privileged instructions and access to descriptors (and their associated segments) within a task. Four-level privilege, as shown in Figure 17, is an extension of the users/supervisor mode commonly found in minicomputers. The privilege levels are numbered 0 through 3. Level 0 is the most privileged level. Privilege levels provide protection within a task. (Tasks are isolated by providing private LDT’s for each task.) Operating system routines, interrupt handlers, and other system software can be included and protected within the virtual address space of each task using the four levels of privilege. Each task in the system has a separate stack for each of its privilege levels. Tasks, descriptors, and selectors have a privilege level attribute that determines whether the descriptor may be used. Task privilege affects the use of instructions and descriptors. Descriptor and selector privilege only affect access to the descriptor. CPU ENFORCED SOFTWARE INTERFACES APPLICATIONS 0 OS EXTENSIONS † MUST BE SET TO 0 FOR COMPATIBILITY WITH FUTURE UPGRADES PL = 3 FIGURE 15. GLOBAL DESCRIPTOR TABLE AND INTERRUPT DESCRlPTOR TABLE DATA TYPE SYSTEM SERVICES Interrupt Descriptor Table The protected mode 80C286 has a third descriptor table, called the Interrupt Descriptor Table (IDT) (see Figure 16), used to define up to 256 interrupts. It may contain only task gates, interrupt gates and trap gates. The IDT (Interrupt Descriptor Table) has a 24-bit physical base and 16-bit limit register in the CPU. The privileged LlDT instruction loads these registers with a six byte value of identical form to that of the LGDT instruction (see Figure 16 and Protected Mode lnitialization). References to IDT entries are made via INT instructions, external interrupt vectors, or exceptions. The IDT must be at least 256 bytes in size to allocate space for all reserved interrupts. FN2947 Rev.3.00 January 28, 2008 GATE FOR INTERRUPT #1 GATE FOR INTERRUPT #0 IDT BASE 0 LDT LIMIT 23 0 INTERRUPT DESCRIPTOR TABLE (IDT) INCREASING MEMORY ADDRESS 15 HIGH SPEED OPERATING SYSTEM INTERFACE PL = 2 PL = 1 KERNAL PL = 0 MOST PRIVILEGED NOTE: PL becomes numerically lower as privilege level increases. FIGURE 17. HIERARCHICAL PRIVILEGE LEVELS Page 20 of 65 80C286 Task Privilege A task always executes at one of the four privilege levels. The task privilege level at any specific instant is called the Current Privilege Level (CPL) and is defined by the lower two bits of the CS register. CPL cannot change during execution in a single code segment. A task's CPL may only be changed by control transfers through gate descriptors to a new code segment (See Control Transfer). Tasks begin executing at the CPL value specified by the code segment selector within TSS when the task is initiated via a task switch operation (See Figure 18). A task executing at Level 0 can access all data segments defined in the GDT and the task's LDT and is considered the most trusted level. A task executing a Level 3 has the most restricted access to data and is considered the least trusted level. Descriptor Privilege Descriptor privilege is specified by the Descriptor Privilege Level (DPL) field of the descriptor access byte. DPL specifies the least trusted task privilege level (CPL) at which a task may access the descriptor. Descriptors with DPL = 0 are the most protected. Only tasks executing at privilege level 0 (CPL = 0) may access them. Descriptors with DPL = 3 are the least protected (i.e. have the least restricted access) since tasks can access them when CPL = 0, 1, 2, or 3). This rule applies to all descriptors, except LDT descriptors. Selector Privilege Selector privilege is specified by the Requested Privilege Level (RPL) field in the least significant two bits of a selector. Selector RPL may establish a less trusted privilege level than the current privilege level for the use of a selector. This level is called the task's effective privilege level (EPL). RPL can only reduce the scope of a task's access to data with this selector. A task's effective privilege is the numeric maximum of RPL and CPL. A selector with RPL = 0 imposes no additional restriction on its use while a selector with RPL = 3 can only refer to segments at privilege Level 3 regardless of the task's CPL. RPL is generally used to verify that pointer parameters passed to a more trusted procedure are not allowed to use data at a more privileged level than the caller (refer to pointer testing instructions). Descriptor Access and Privilege Validation Determining the ability of a task to access a segment involves the type of segment to be accessed, the instruction used, the type of descriptor used and CPL, RPL, and DPL. The two basic types of segment accesses are control transfer (selectors loaded into CS) and data (selectors loaded into DS, ES or SS). Data Segment Access Instructions that load selectors into DS and ES must refer to a data segment descriptor or readable code segment descriptor. The CPL of the task and the RPL of the selector must be the same as or more privileged (numerically equal to or lower than) than the descriptor DPL. In general, a task can only access data segments at the same or less privileged levels than the CPL or RPL (whichever is numerically higher) to prevent a program from accessing data it cannot be trusted to use. An exception to the rule is a readable conforming code segment. This type of code segment can be read from any privilege level. If the privilege checks fail (e.g. DPL is numerically less than the maximum of CPL and RPL) or an incorrect type of descriptor is referenced (e.g. gate descriptor or execute only code segment) exception 13 occurs. If the segment is not present, exception 11 is generated. Instructions that load selectors into SS must refer to data segment descriptors for writable data segments. The descriptor privilege (DPL) and RPL must equal CPL. All other descriptor types or a privilege level violation will cause exception 13. A not present fault causes exception 12. TABLE 13. DESCRlPTOR TYPES USED FOR CONTROL TRANSFER CONTROL TRANSFER TYPES OPERATION TYPES DESCRIPTOR REFERENCED DESCRIPTOR TABLE Intersegment within the same privilege levels JMP, CALL, RET, lRET (Note 4) Code Segment GDT/LDT Intersegment to the same or higher privilege level interrupt within task may change CPL CALL Call Gate GDT/LDT Interrupt Instruction, Exception External Interrupt Trap or Interrupt Gate lDT Intersegment to a lower privilege level (changes task CPL) RET, IRET (Note 4) Code Segment GDT/LDT Task Switch CALL, JMP Task State Segment GDT CALL, JMP Task Gate GDT/LDT lRET (Note 5) Interrupt Instruction, Exception External Interrupt Task Gate IDT NOTES: 4. NT (Nested Task bit of flag word) = 0 5. NT (Nested Task bit of flag word) = 1 FN2947 Rev.3.00 January 28, 2008 Page 21 of 65 80C286 Control Transfer Privilege Level Changes Four types of control transfer can occur when a selector is loaded into CS by a control transfer operation (see Table 13). Each transfer type can only occur if the operation which loaded the selector references the correct descriptor type. Any violation of these descriptor usage rules (e.g. JMP through a call gate or RET to a Task State Segment) will cause exception 13. Any control transfer that changes CPL within the task, causes a change of stacks as part of the operation. Initial values of SS:SP for privilege levels 0, 1, and 2 are kept in the task state segment (refer to Task Switch Operation). During a JMP or CALL control transfer, the new stack pointer is loaded into the SS and SP registers and the previous stack pointer is pushed onto the new stack. The ability to reference a descriptor for control transfer is also subject to rules of privilege. A CALL or JUMP instruction may only reference a code segment descriptor with DPL equal to the task CPL or a conforming segment with DPL of equal or greater privilege than CPL. The RPL of the selector used to reference the code descriptor must have as much privilege as CPL. RET and IRET instructions may only reference code segment descriptors with descriptor privilege equal to or less privileged than the task CPL. The selector loaded into CS is the return address from the stack. After the return, the selector RPL is the task's new CPL. If CPL changes, the old stack pointer is popped after the return address. When a JMP or CALL references a Task State Segment descriptor, the descriptor DPL must be the same or less privileged than the task's CPL. Reference to a valid Task State Segment descriptor causes a task switch (see Task Switch Operation). Reference to a Task State Segment descriptor at a more privileged level than the task's CPL generates exception 13. When an instruction or interrupt references a gate descriptor, the gate DPL must have the same or less privilege than the task CPL. If DPL is at a more privileged level than CPL, exception 13 occurs. If the destination selector contained in the gate references a code segment descriptor, the code segment descriptor DPL must be the same or more privileged than the task CPL. If not, Exception 13 is issued. After the control transfer, the code segment descriptors DPL is the task's new CPL. If the destination selector in the gate references a task state segment, a task switch is automatically performed (see Task Switch Operation). The privilege rules on control transfer require: • JMP or CALL direct to a code segment (code segment descriptor) can only be a conforming segment with DPL of equal or greater privilege than CPL or a non-conforming segment at the same privilege level. • Interrupts within the task, or calls that may change privilege levels, can only transfer control through a gate at the same or a less privileged level than CPL to a code segment at the same or more privileged level than CPL. • Return instructions that don't switch tasks can only return control to a code segment at the same or less privileged level. • Task switch can be performed by a call, jump or interrupt which references either a task gate or task state segment at the same or less privileged level. FN2947 Rev.3.00 January 28, 2008 When returning to the original privilege level, its stack is restored as part of the RET or IRET instruction operation. For subroutine calls that pass parameters on the stack and cross privilege levels, a fixed number of words, as specified in the gate, are copied from the previous stack to the current stack. The inter-segment RET instruction with a stack adjustment value will correctly restore the previous stack pointer upon return. Protection The 80C286 includes mechanisms to protect critical instructions that effect the CPU execution state (e.g. HLT) and code or data segments from improper usage. These protection mechanisms are grouped into three forms: • Restricted usage of segments (e.g. no write allowed to readonly data segments). The only segments available for use are defined by descriptors in the Local Descriptor Table (LDT) and Global Descriptor Table (GDT). • Restricted access to segments via the rules of privilege and descriptor usage. • Privileged instructions or operations that may only be executed at certain privilege levels as determined by the CPL and I/O Privilege Level (lOPL). The lOPL is defined by bits 14 and 13 of the flag word. These checks are performed for all instructions and can be split into three categories: segment load checks (Table 14), operand reference checks (Table 15), and privileged instruction checks (Table 16). Any violation of the rules shown will result in an exception. A not-present exception related to the stack segment causes exception 12. TABLE 14. SEGMENT REGISTER LOAD CHECKS EXCEPTION NUMBER ERROR DESCRIPTION Descriptor table limit exceeded 13 Segment descriptor not-present 11 or 12 Privilege rules violated 13 Invalid descriptor/segment type segment register load: - Read only data segment load to SS - Special control descriptor load to DS, ES, SS - Execute only Segment load to DS, ES, SS - Data segment load to CS - Read/Execute code segment load SS 13 Page 22 of 65 80C286 TABLE 15. OPERAND REFERENCE CHECKS EXCEPTION NUMBER ERROR DESCRIPTION Write into code segment 13 Read from execute-only code segment 13 Write to read-only data segment 13 Segment limit exceeded (See Note) 12 or 13 NOTE: Carry out in offset calculations is ignored. TABLE 16. PRIVILEGED INSTRUCTION CHECKS EXCEPTION NUMBER ERROR DESCRIPTION CPL 0 when executing the following instructions: LIDT, LLDT, LGDT, LTR, LMSW, CTS, HLT 13 CPT > IOPL when executing the following instructions: INS, IN, OUTS, OUT, STI, CLI, LOCK 13 The lRET and POPF instructions do not perform some of their defined functions if CPL is not of sufficient privilege (numerically small enough). Precisely these are: • The IF bit is not changed if CPL is greater than IOPL. • The lOPL field of the flag word is not changed if CPL is greater than 0. No exceptions or other indication are given when these conditions occur. Exceptions The 80C286 detects several types of exceptions and interrupts in protected mode (see Table 17). Most are restartable after the exceptional condition is removed. Interrupt handlers for most exceptions can read an error code, pushed on the stack after the return address, that identifies the selector involved (0 if none). The return address normally points to the failing instruction including all leading prefixes. For a processor extension segment overrun exception, the return address will not point at the ESC instruction that caused the exception; however, the processor extension registers may contain the address of the failing instruction. These exceptions indicate a violation to privilege rules or usage rules has occurred. Restart is generally not attempted under those conditions. All these checks are performed for all instructions and can be split into three categories: segment load checks (Table 14), operand reference checks (Table 15), and privileged instruction checks (Table 16). Any violation of the rules shown will result in an exception. A not-present exception causes exception 11 or 12 and is restartable. SPECIAL OPERATIONS Task Switch Operation The 80C286 provides a built-in task switch operation which saves the entire 80C286 execution state (registers, address space, and a link to the previous task), loads a new execution state, and commences execution in the new task. Like gates, the task switch operation is invoked by executing an inter-segment JMP or CALL instruction which refers to a Task State Segment (TSS) or task gate descriptor in the GDT or LDT. An INT instruction, exception, or external interrupt may also invoke the task switch operation by selecting a task gate descriptor in the associated IDT descriptor entry. The TSS descriptor points at a segment (see Figure 18) containing the entire 80C286 execution state while a task gate descriptor contains a TSS selector. The limit field of the descriptor must be greater than 002B(H). Each task must have a TSS associated with it. The current TSS is identified by a special register in the 80C286 called the Task Register (TR). This register contains a selector referring to the task state segment descriptor that defines the current TSS. A hidden base and limit register associated with TR are loaded whenever TR is loaded with a new selector. The IRET instruction is used to return control to the task that called the current task or was interrupted. Bit 14 in the flag register is called the Nested Task (NT) bit. It controls the TABLE 17. PROTECTED MODE EXCEPTIONS INTERRUPT VECTOR FUNCTION RETURN ADDRESS AT FALLING INSTRUCTION? ALWAYS RESTARTABLE? ERROR CODE ON STACK? 8 Double exception detected Yes No (Note 7) Yes 9 Processor extension segment overrun No No (Note 7) No 10 Invalid task state segment Yes Yes Yes 11 Segment not present Yes Yes Yes 12 Stack segment overrun or stack segment not present Yes Yes (Note 6) Yes 13 General protection Yes No (Note 7) Yes NOTES: 6. When a PUSHA or POPA instruction attempts to wrap around the stack segment, the machine state after the exception will not be restartable because stack segment wrap around is not permitted. This condition is identified by the value of the saved SP being either 0000(H), 0001(H), FFFE(H), or FFFF(H). 7. These exceptions indicate a violation to privilege rules or usage rules has occurred. Restart is generally not attempted under those conditions. FN2947 Rev.3.00 January 28, 2008 Page 23 of 65 80C286 function of the IRET instruction. If NT = 0, the IRET instruction performs the regular current task by popping values off the stack; when NT = 1, IRET performs a task switch operation back to the previous task. When a CALL, JMP, or INT instruction initiates a task switch, the old (except for case of JMP) and new TSS will be marked busy and the back link field of the new TSS set to the old TSS selector. The NT bit of the new task is set by CALL or INT initiated task switches. An interrupt that does not cause a task switch will clear NT. NT may also be set or cleared by POPF or IRET instructions. The task state segment is marked busy by changing the descriptor type field from Type 1 to Type 3. Use of a selector that references a busy task state segment causes Exception 13. Processor Extension Context Switching The context of a processor extension is not changed by the task switch operation. A processor extension context need only be changed when a different task attempts to use the processor extension (which still contains the context of a previous task). The 80C286 detects the first use of a processor extension after a task switch by causing the processor extension not present exception (7). The interrupt handler may then decide whether a context change is necessary. Whenever the 80C286 switches tasks, it sets the Task Switched (TS) bit of the MSW. TS indicates that a processor extension context may belong to a different task than the current one. The processor extension not present exception (7) will occur when attempting to execute an ESC or WAIT instruction if TS = 1 and a processor extension is present (MP = 1 in MSW). Pointer Testing Instructions The 80C286 provides several instructions to speed pointer testing and consistency checks for maintaining system integrity (see Table 18). These instructions use the memory management hardware to verify that a selector value refers to an appropriate segment without risking an exception. A condition flag (ZF) indicates whether use of the selector or segment will cause an exception. Double Fault and Shutdown If two separate exceptions are detected during a single instruction execution, the 80C286 performs the double fault exception (8). If an exception occurs during processing of the double fault exception, the 80C286 will enter shutdown. During shutdown no further instructions or exceptions are processed. Either NMI (CPU remains in protected mode) or RESET (CPU exits protected mode) can force the 80C286 out of shutdown. Shutdown is externally signalled via a HALT bus operation with A1 LOW. Protected Mode lnitialization The 80C286 initially executes in real address mode after RESET. To allow initialization code to be placed at the top of physical memory. A23-20 will be HIGH when the 80C286 performs memory references relative to the CS register until CS is changed. A23-20 will be zero for references to the DS, ES, or SS segments. Changing CS in real address mode will force A23-20 LOW whenever CS is used again. The initial CS:lP value of F000:FFF0 provides 64K bytes of code space for initialization code without changing CS. Protected mode operation requires several registers to be initialized. The GDT and IDT base registers must refer to a valid GDT and IDT. After executing the LMSW instruction to set PE, the 80C286 must immediately execute an intrasegment JMP instruction to clear the instruction queue of instructions decoded in real address mode. To force the 80C286 CPU registers to match the initial protected mode state assumed by software, execute a JMP instruction with a selector referring to the initial TSS used in the system. This will load the task register, local descriptor table register, segment registers and initial general register state. The TR should point at a valid TSS since any task switch operation involves saving the current task state. TABLE 18. 80C286 POINTER TEST INSTRUCTIONS INSTRUCTION OPERANDS FUNCTION ARPL Selector, Register Adjust Requested Privilege Level: adjusts the RPL of the selector to the numeric maximum of current selector RPL value and the RPL value in the register. Set zero flag if selector RPL was changed by ARPL. VERR Selector VERify for Read: sets the zero flag if the segment referred to by the selector can be read. VERW Selector VERify for Write: sets the zero flag if the segment referred to by the selector can be written. LSL Register, Selector Load Segment Limit: reads the segment limit into the register if privilege rules and descriptor type allow. Set zero flag if successful. LAR Register, Selector Load Access Rights: reads the descriptor access rights byte into the register if privilege rules allow. Set zero flag if successful. FN2947 Rev.3.00 January 28, 2008 Page 24 of 65 80C286 CPU RESERVED TASK REGISTER TR 15 0 SYSTEM SEGMENT DESCRIPTOR P D 0 TYPE P L BASE 23 - 16 DESCRIPTION 1 An available task state segment. May be used as the destination of a task switch operation. 3 A busy task state segment. Cannot be used as the destination of a task switch. DESCRIPTION BASE 15 - 0 PROGRAM INVISIBLE 15 TYPE LIMIT 15 - 0 0 LIMIT BASE 23 0 15 TASK STATE SEGMENT 0 BYTE OFFSET TASK LDT SELECTOR 42 DS SELECTOR 40 P SS SELECTOR 38 1 Base and Limit fields are valid. CS SELECTOR 36 ES SELECTOR 0 34 DI 32 Segment is not present in memory, Base and Limit are not defined. SI 30 BP 28 SP 26 BX 24 DX 22 CX 20 AX 18 FLAG WORD 16 IP (ENTRY POINT) 14 SS FOR CPL 2 12 SP FOR CPL 2 10 SS FOR CPL 1 8 SP FOR CPL 1 6 SS FOR CPL 0 4 SP FOR CPL 0 2 CURRENT TASK STATE INITIAL STACKS FOR CPL 0, 1, 2 BACK LINK SELECTOR TO TSS 0 FIGURE 18. TASK STATE SEGMENT AND TSS REGISTERS FN2947 Rev.3.00 January 28, 2008 Page 25 of 65 80C286 System Interface The 80C286 system interface appears in two forms: a local bus and a system bus. The local bus consists of address, data, status, and control signals at the pins of the CPU. A system bus is any buffered version of the local bus. A system bus may also differ from the local bus in terms of coding of status and control lines and/or timing and loading of signals. OUTPUT DRIVER BOND PAD VCC EXTERNAL PIN P Bus Interface Signals and Timing The 80C286 microsystems local bus interfaces the 80C286 to local memory and I/O components. The interface has 24 address lines, 16 data lines, and 8 status and control signals. The 80C286 CPU, 82C284 clock generator, 82C288 bus controller, 82289 bus arbiter, 82C86H/87H transceivers, and 82C82/83H latches provide a buffered and decoded system bus interface. The 82C284 generates the system clock and synchronizes READY and RESET. The 82C288 converts bus operation status encoded by the 80C286 into command and bus control signals. The 82289 bus arbiter generates Multibus™ bus arbitration signals. These components can provide the critical timing required for most system bus interfaces including the Multibus. Bus Hold Circuitry To avoid high current conditions caused by floating inputs to CMOS devices, and to eliminate the need for pull-up/down resistors, “bus-hold” circuitry has been used on the 80C286 pins 4-6, 36-51 and 66-68 (See Figure 19A and 19B). The circuit shown in Figure 19A will maintain the last valid logic state if no driving source is present (i.e. an unconnected pin or a driving source which goes to a high impedance state). The circuit shown in Figure 19B will maintain a high impedance logic one state if no driving source is present. To overdrive the “bushold” circuits, an external driver must be capable of sinking or sourcing approximately 400 microamps at valid input voltage levels. Since this “bus-hold” circuitry is active and not a “resistive” type element, the associated power supply current is negligible, and power dissipation is significantly reduced when compared to the use of passive pull-up resistors. BOND PAD EXTERNAL PIN OUTPUT DRIVER INPUT DRIVER INPUT PROTECTION CIRCUITRY FIGURE 19B. BUS HOLD CIRCUITRY, PINS 4-6, 68 Physical Memory and I/O Interface A maximum of 16 megabytes of physical memory can be addressed in protected mode. One megabyte can be addressed in real address mode. Memory is accessible as bytes or words. Words consist of any two consecutive bytes addressed with the least significant byte stored in the lowest address. Byte transfers occur on either half of the 16-bit local data bus. Even bytes are accessed over D7-0 while odd bytes are transferred over D15-8. Even addressed words are transferred over D15-0 in one bus cycle, while odd addressed word require two bus operations. The first transfers data on D15-8, and the second transfers data on D7-0. Both byte data transfers occur automatically, transparent to software. Two bus signals, A0 and BHE, control transfers over the lower and upper halves of the data bus. Even address byte transfers are indicated by A0 LOW and BHE HIGH. Odd address byte transfers are indicated by A0 HlGH and BHE LOW. Both A0 and BHE are LOW for even address word transfers. The I/O address space contains 64K addresses in both modes. The I/O space is accessible as either bytes or words, as is memory. Byte wide peripheral devices may be attached to either the upper or lower byte of the data bus. Byte-wide I/O devices attached to the upper data byte (D15-8) are accessed with odd I/O addresses. Devices on the lower data byte are accessed with even I/O addresses. An interrupt controller such as Intersil's 82C59A must be connected to the lower data byte (D7-0) for proper return of the interrupt vector. Bus Operation INPUT PROTECTION CIRCUITRY FIGURE 19A. BUS HOLD CIRCUITRY, PINS 36-51, 66, 67 FN2947 Rev.3.00 January 28, 2008 INPUT DRIVER The 80C286 uses a double frequency system clock (CLK input) to control bus timing. All signals on the local bus are measured relative to the system CLK input. The CPU divides the system clock by 2 to produce the internal processor clock, which determines bus state. Each processor clock is composed of two system clock cycles named phase 1 and phase 2. The 82C284 clock generator output (PCLK) identifies the next phase of the processor clock. (See Figure 20.) Page 26 of 65 80C286 During hold (TH), the 80C286 will float all address, data, and status output drivers enabling another bus master to use the local bus. The 80C286 HOLD input signal is used to place the 80C286 into the TH state. The 80C286 HLDA output signal indicates that the CPU has entered TH. ONE PROCESSOR CLOCK CYCLE ONE BUS T STATE PHASE 1 OF PROCESSOR CLOCK CYCLE PHASE 2 OF PROCESSOR CLOCK CYCLE Pipelined Addressing CLK ONE SYSTEM CLK CYCLE PCLK FIGURE 20. SYSTEM AND PROCESSOR CLOCK RELATIONSHIPS Six types of bus operations are supported; memory read, memory write, I/O read, I/O write, interrupt acknowledge, and halt/shutdown. Data can be transferred at a maximum rate of one word per two processor clock cycles. The 80C286 bus has three basic states: idle (TI), send status (TS), and perform command (TC). The 80C286 CPU also has a fourth local bus state called hold (TH). TH indicates that the 80C286 has surrendered control of the local bus to another bus master in response to a HOLD request. Each bus state is one processor clock long. Figure 21 shows the four 80C286 local bus states and allowed transitions. RESET HLDA NEW CYCLE HLDA HLDA HOLD TH IDLE TI HLDA NEW CYCLE READY NEW CYCLE NEW CYCLE READY HLDA NEW CYCLE ALWAYS STATUS TS COMMAND TC READY NEW CYCLE FIGURE 21. 80C286 BUS STATES Bus States The idle (TI) state indicates that no data transfers are in progress or requested. The first active state TS is signaled by status line S1 or S0 going LOW and identifying phase 1 of the processor clock. During TS, the command encoding, the address, and data (for a write operation) are available on the 80C286 output pins. The 82C288 bus controller decodes the status signals and generates Multibus compatible read/write command and local transceiver control signals. After TS, the perform command (TC) state is entered. Memory or I/O devices respond to the bus operation during TC , either transferring read data to the CPU or accepting write data. TC states may be repeated as often as necessary to ensure sufficient time for the memory or I/O device to respond. The READY signal determines whether TC is repeated. A repeated TC state is called a wait state. FN2947 Rev.3.00 January 28, 2008 The 80C286 uses a local bus interface with pipelined timing to allow as much time as possible for data access. Pipelined timing allows a new bus operation to be initiated every two processor cycles, while allowing each individual bus operation to last for three processor cycles. The timing of the address outputs is pipelined such that the address of the next bus operation becomes available during the current bus operation. Or, in other words, the first clock of the next bus operation is overlapped with the last clock of the current bus operation. Therefore, address decode and routing logic can operate in advance of the next bus operation. External address latches may hold the address stable for the entire bus operation, and provide additional AC and DC buffering. The 80C286 does not maintain the address of the current bus operation during all TC states. Instead, the address for the next bus operation may be emitted during phase 2 of any TC . The address remains valid during phase 1 of the first TC to guarantee hold time, relative to ALE, for the address latch inputs. Bus Control Signals The 82C288 bus controller provides control signals; address latch enable (ALE), Read/Write commands, data transmit/receive (DT/R), and data enable (DEN) that control the address latches, data transceivers, write enable, and output enable for memory and I/O systems. The Address Latch Enable (ALE) output determines when the address may be latched. ALE provides at least one system CLK period of address hold time from the end of the previous bus operation until the address for the next bus operation appears at the latch outputs. This address hold time is required to support Multibus and common memory systems. The data bus transceivers are controlled by 82C288 outputs Data Enable (DEN) and Data Transmit/Receive (DT/R). DEN enables the data transceivers; while DT/R controls transceiver direction. DEN and DT/R are timed to prevent bus contention between the bus master, data bus transceivers, and system data bus transceivers. Command Timing Controls Two system timing customization options, command extension and command delay, are provided on the 80C286 local bus. Command extension allows additional time for external devices to respond to a command and is analogous to inserting wait states on the 80C86. External logic can control the duration of any bus operation such that the operation is only as long as necessary. The READY input signal can extend any bus operation for as long as necessary. Command delay allows an increase of address or write data Page 27 of 65 80C286 less. To customize system bus timing, an address decoder can determine which bus operations require delaying the command. The CMDLY input does not affect the timing of ALE, DEN or DT/R. setup time to system bus command active for any bus operation by delaying when the system bus command becomes active. Command delay is controlled by the 82C288 CMDLY input. After TS, the bus controller samples CMDLY at each failing edge of CLK. If CMDLY is HIGH, the 82C288 will not activate the command signal. When CMDLY is LOW, the 82C288 will activate the command signal. After the command becomes active, the CMDLY input is not sampled. Figure 23 illustrates four uses of CMDLY. Example 1 shows delaying the read command two system CLKs for cycle N-1 and no delay for cycle N, and example 2 shows delaying the read command one system CLK for cycle N-1 and one system CLK delay for cycle N. When a command is delayed, the available response time from command active to return read data or accept write data is READ BUS CYCLE N TI TS 1 READ BUS CYCLE N + 1 TC 2 1 TS 2 1 TC 2 1 2 CLK PROC CLK 2 PCLK CYCLE TRANSFER 2 PCLK CYCLE TRANSFER 2.5 CLOCK CYCLE ADDRESS TO DATA VALID A23 - A0 VALID ADDR (N) VALID ADDR (N + 1) S0  S1 READY D15 - D0 VALID READ DATA (N) VALID READ DATA (N + 1) PIPELINING: VALID ADDRESS (N + 1) AVAILABLE IN LAST PHASE OF BUS CYCLE (N). FIGURE 22. BASIC BUS CYCLE FN2947 Rev.3.00 January 28, 2008 Page 28 of 65 80C286 READ CYCLE N -1 TS 1 READ CYCLE N TC 2 1 TC 2 1 TS 2 1 TC 2 1 2 CLK PROC CLK A23 - A0 VALID ADDR (N-1) VALID ADDR N S1 S0 ALE READY RD EX1 CMDLY RD EX2 CMDLY FIGURE 23. CMDLY CONTROLS THE LEADING EDGE OF COMMAND SIGNAL Bus Cycle Termination At maximum transfer rates, the 80C286 bus alternates between the status and command states. The bus status signals become inactive after TS so that they may correctly signal the start of the next bus operation after the completion of the current cycle. No external indication of TC exists on the 80C286 local bus. The bus master and bus controller enter TC directly after TS and continue executing TC cycles until terminated by the assertion of READY. READY Operation The current bus master and 82C288 bus controller terminate each bus operation simultaneously to achieve maximum bus operation bandwidth. Both are informed in advance by READY active (open-collector output from 82C284) which identifies the last TC cycle of the current bus operation. The bus master and bus controller must see the same sense of the READY signal, thereby requiring READY to be synchronous to the system clock. Synchronous Ready The 82C284 clock generator provides READY synchronization from both synchronous and asynchronous sources (see Figure 24). The synchronous ready input (SRDY) of the clock generator is sampled with the falling edge of CLK at the end of phase FN2947 Rev.3.00 January 28, 2008 1 of each TC. The state of SRDY is then broadcast to the bus master and bus controller via the READY output line. Asynchronous Ready Many systems have devices or subsystems that are asynchronous to the system clock. As a result, their ready outputs cannot be guaranteed to meet the 82C284 SRDY setup and hold time requirements. But the 82C284 asynchronous ready input (ARDY) is designed to accept such signals. The ARDY input is sampled at the beginning of each TC cycle by 82C284 synchronization logic. This provides one system CLK cycle time to resolve its value before broadcasting it to the bus master and bus controller. ARDY or ARDYEN must be HIGH at the end of TS. ARDY cannot be used to terminate the bus cycle with no wait states. Each ready input of the 82C284 has an enable pin (SRDYEN and ARDYEN) to select whether the current bus operation will be terminated by the synchronous or asynchronous ready. Either of the ready inputs may terminate a bus operation. These enable inputs are active low and have the same timing as their respective ready inputs. Address decode logic usually selects whether the current bus operation should be terminated by ARDY or SRDY. Data Bus Control Page 29 of 65 80C286 Figures 25, 26, and 27 show how the DT/R, DEN, data bus, and address signals operate for different combinations of read, write, and idle bus operations. DT/R goes active (LOW) for a read operation. DT/R remains HIGH before, during, and between write operations. The data bus is driven with write data during the second phase of TS . The delay in write data timing allows the read data drivers, from a previous read cycle, sufficient time to enter threestate OFF before the 80C286 CPU begins driving the local data bus for write operations. Write data will always remain valid for one system clock past the last TC to provide sufficient hold time for Multibus or other similar memory or I/O systems. During write-read or write-idle sequences the data bus enters a high impedance state during the second phase of the processor cycle after the last TC . In a write-write sequence the data bus does not enter a high impedance state between TC and TS. Bus Usage The 80C286 local bus may be used for several functions: instruction data transfers, data transfers by other bus masters, instruction fetching, processor extension data transfers, interrupt acknowledge, and halt/shutdown. This section describes local bus activities which have special signals or requirements. Note that I/O transfers take place in exactly the same manner as memory transfers (i.e. to the 80C286 the timing, etc. of an I/O transfer is identical to a memory transfer). HOLD and HLDA HOLD and HLDA allow another bus master to gain control of the local bus by placing the 80C286 bus into the TH state. The sequence of events required to pass control between the 80C286 and another local bus master are shown in Figure 28. In this example, the 80C286 is initially in the TH state as signaled by HLDA being active. Upon leaving TH, as signaled by HLDA going inactive, a write operation is started. During the write operation another local bus master requests the local bus from the 80C286 as shown by the HOLD signal. After completing the write operation, the 80C286 performs one TI bus cycle, to guarantee write data hold time, then enters TH as signaled by HLDA going active. prefix is used. The LOCK prefix may be used with the following ASM-286 assembly instructions; MOVS, INS and OUTS. For bus cycles other than Interrupt-Acknowledge cycles, Lock will be active for the first and subsequent cycles of a series of cycles to be locked. Lock will not be shown active during the last cycle to be locked. For the next-to-last cycle, Lock will become inactive at the end of the first TC regardless of the number of wait states inserted. For Interrupt-Acknowledge cycles, Lock will be active for each cycle, and will become inactive at the end of the first TC for each cycle regardless of the number of wait-states inserted. Instruction Fetching The 80C286 Bus Unit (BU) will fetch instructions ahead of the current instruction being executed. This activity is called prefetching. It occurs when the local bus would otherwise be idle and obeys the following rules: A prefetch bus operation starts when at least two bytes of the 6-byte prefetch queue are empty. The prefetcher normally performs word prefetches independent of the byte alignment of the code segment base in physical memory. The prefetcher will perform only a byte code fetch operation for control transfers to an instruction beginning on a numerically odd physical address. Prefetching stops whenever a control transfer or HLT instruction is decoded by the lU and placed into the instruction queue. In real address mode, the prefetcher may fetch up to 6 bytes beyond the last control transfer or HLT instruction in a code segment. In protected mode, the prefetcher will never cause a segment overrun exception. The prefetcher stops at the last physical memory word of the code segment. Exception 13 will occur if the program attempts to execute beyond the last full instruction in the code segment. If the last byte of a code segment appears on an even physical memory address, the prefetcher will read the next physical byte of memory (perform a word code fetch). The value of this byte is ignored and any attempt to execute it causes exception 13. The CMDLY signal and ARDY ready are used to start and stop the write bus command, respectively. Note that SRDY must be inactive or disabled by SRDYEN to guarantee ARDY will terminate the cycle. HOLD must not be active during the time from the leading edge of RESET until 34 CLKs following the trailing edge of RESET unless the 80C286 is in the Halt condition. To ensure that the 80C286 remains in the Halt condition until the processor Reset operation is complete, no interrupts should occur after the execution of HLT until 34 CLKs after the trailing edge of the RESET pulse. LOCK The CPU asserts an active lock signal during InterruptAcknowledge cycles, the XCHG instruction, and during some descriptor accesses. Lock is also asserted when the LOCK FN2947 Rev.3.00 January 28, 2008 Page 30 of 65 80C286 MEMORY CYCLE N - 1 TS 1 MEMORY CYCLE N TC 2 1 TS 2 1 TC 2 1 TC 2 1 2 CLK PROC CLK A23 - A0 VALID ADDR VALID ADDR VALID ADDR S0 S1 SRDY READY (SEE NOTE 8) (SEE NOTE 9) ARDY (SEE NOTE 10) NOTES: 8. SRDYEN is active low. 9. If SRDYEN is high, the state of SRDY will not effect READY. 10. ARDYEN is active low. FIGURE 24. SYNCHRONOUS AND ASYNCHRONOUS READY FN2947 Rev.3.00 January 28, 2008 Page 31 of 65 80C286 READ CYCLE TI TS 2 1 WRITE CYCLE TC 2 1 TS 2 1 TC 2 1 TI 2 1 2 CLK A23 - A0 VALID ADDR VALID ADDR S0 S1 D15 - D0 VALID WRITE DATA VALID READ DATA MRDC MWTC DEN DT/R FIGURE 25. BACK TO BACK READ-WRITE CYCLE FN2947 Rev.3.00 January 28, 2008 Page 32 of 65 80C286 WRITE CYCLE TI READ CYCLE TS 2 1 TC 2 1 TS 2 1 TC 2 1 TI 2 1 2 CLK A23 - A0 VALID VALID S0 S1 VALID READ DATA VALID WRITE DATA D15 - D0 MRDC MWTC DEN DT/R FIGURE 26. BACK TO BACK WRITE-READ CYCLE WRITE CYCLE N-1 TI TS 2 1 WRITE CYCLE N TC 2 1 TS 2 1 TC 2 1 TI 2 1 2 CLK A23 - A0 VALID ADDR N-1 VALID ADDR N S0 S1 D15 - D0 VALID DATA N-1 VALID DATA N MWTC DEN (HIGH) DT/R FIGURE 27. BACK TO BACK WRITE-WRITE CYCLE Processor Extension Transfers FN2947 Rev.3.00 January 28, 2008 Page 33 of 65 80C286 The processor extension interface uses I/O port addresses 00F8(H), and 00FC(H) which are part of the I/O port address range reserved by Intersil. An ESC instruction with Machine Status Word bits EM = 0 and TS = 0 will perform I/O bus operations to one or more of these I/O port addresses independent of the value of lOPL and CPL. ESC instructions with memory references enable the CPU to accept PEREQ inputs for processor extension operand transfers. The CPU will determine the operand starting address and read/write status of the instruction. For each operand transfer, two or three bus operations are performed, one word transfer with I/O port address 00FA(H) and one or two bus operations with memory. Three bus operations are required for each word operand aligned on an odd byte address. Interrupt Acknowledge Sequence Figure 29 illustrates an interrupt acknowledge sequence performed by the 80C286 in response to an INTR input. An interrupt acknowledge sequence consists of two INTA bus operations. The first allows a master 82C59A Programmable Interrupt Controller (PlC) to determine which if any of its slaves should return the interrupt vector. An eight bit vector is read on D0-D7 of the 80C286 during the second INTA bus operation to select an interrupt handler routine from the interrupt table. FN2947 Rev.3.00 January 28, 2008 The Master Cascade Enable (MCE) signal of the 82C288 is used to enable the cascade address drivers during INTA bus operations (See Figure 29) onto the local address bus for distribution to slave interrupt controllers via the system address bus. The 80C286 emits the LOCK signal (active LOW) during TS of the first INTA bus operation. A local bus “hold” request will not be honored until the end of the second INTA bus operation. Three idle processor clocks are provided by the 80C286 between INTA bus operations to allow for the minimum INTA to INTA time and CAS (cascade address) out delay of the 82C59A. The second INTA bus operation must always have at least one extra TC state added via logic controlling READY. A23-A0 are in three-state OFF until after the first TC state of the second INTA bus operation. This prevents bus contention between the cascade address drivers and CPU address drivers. The extra TC state allows time for the 80C286 to resume driving the address lines for subsequent bus operations. Page 34 of 65 80C286 BUS HOLD ACKNOWLEDGE BUS CYCLE TYPE TH 1 TH 2 1 TS TH 2 1 BUS HOLD ACKNOWLEDGE WRITE CYCLE 2 1 TC 2 1 TC 2 1 TC 2 1 TI 2 1 TH 2 1 2 CLK (SEE NOTE 15) (SEE NOTE 14) HOLD (SEE NOTE 16) HLDA (SEE NOTE 11) 80C286 (SEE NOTE 11) S1 S0 (SEE NOTE 12) A23 - A0 M/IO, COD/INTA VALID (SEE NOTE 13) BHE, LOCK VALID 80C284 D15 - D0 VALID SRDY + SRDYEN NOT READY NOT READY (SEE NOTE 17) ARDY + ARDYEN NOT READY NOT READY READY CMDLY DELAY ENABLE (SEE NOTE 17) 80C288 MWTC VOH DT/R DEN ALE TS - STATUS CYCLE TC - COMMAND CYCLE NOTES: 11. Status lines are held at a high impedance logic one by the 80C286 during a HOLD state. 12. Address, M/IO and COD/lNTA may start floating during any TC depending on when internal 80C286 bus arbiter decides to release bus to external HOLD. The float starts in 2 of TC. 13. BHE and LOCK may start floating after the end of any TC depending on when internal 80C286 bus arbiter decides to release bus to external HOLD. The float starts in 1 of TC. 14. The minimum HOLD to HLDA time is shown. Maximum is one TH longer. 15. The earliest HOLD time is shown. It will always allow a subsequent memory cycle if pending is shown. 16. The minimum HOLD to HLDA time is shown. Maximum is a function of the instruction, type of bus cycle and other machine state (i.e., Interrupts, Waits, Lock, etc.). 17. Asynchronous ready allows termination of the cycle. Synchronous ready does not signal ready in this example. Synchronous ready state is ignored after ready is signaled via the asynchronous input. FIGURE 28. MULTIBUS WRITE TERMINATED BY ASYNCHRONOUS READY WITH BUS HOLD FN2947 Rev.3.00 January 28, 2008 Page 35 of 65 80C286 Local Bus Usage Priorities System Configurations The 80C286 local bus is shared among several internal units and external HOLD requests. In case of simultaneous requests, their relative priorities are: The versatile bus structure of the 80C286 micro-system, with a full complement of support chips, allows flexible configuration of a wide range of systems. The basic configuration, shown in Figure 30, is similar to an 80C86 maximum mode system. It includes the CPU plus an 82C59A interrupt controller, 82C284 clock generator, and the 82C288 Bus Controller. The 80C86 latches (82C82 and 82C83H) and transceivers (82C86H and 82C87H) may be used in an 80C286 microsystem. (Highest) Any transfers which assert LOCK either explicitly (via the LOCK instruction prefix) or implicitly (i.e. some segment descriptor accesses, an interrupt acknowledge sequence, or an XCHG with memory). The second of the two byte bus operations required for an odd aligned word operand. The second or third cycle of a processor extension data transfer. Local bus request via HOLD input. Processor extension data operand transfer via PEREQ input. Data transfer performed by EU as part of an instruction. (Lowest) An instruction prefetch request from BU. The EU will inhibit prefetching two processor clocks in advance of any data transfers to minimize waiting by the EU for a prefetch to finish. Halt or Shutdown Cycles The 80C286 externally indicates halt or shutdown conditions as a bus operation. These conditions occur due to a HLT instruction or multiple protection exceptions while attempting to execute one instruction. A halt or shutdown bus operation is signalled when S1, S0 and COD/lNTA are LOW and M/IO is HIGH. A1 HIGH indicates halt, and A1 LOW indicates shutdown. The 82C288 bus controller does not issue ALE, nor is READY required to terminate a halt or shutdown bus operation. During halt or shutdown, the 80C286 may service PEREQ or HOLD requests. A processor extension segment overrun during shutdown will inhibit further service of PEREQ. Either NMl or RESET will force the 80C286 out of either halt or shutdown. An INTR, if interrupts are enabled, or a processor extension segment overrun exception will also force the 80C286 out of halt. As indicated by the dashed lines in Figure 30, the ability to add processor extensions is an integral feature of 80C286 based microsystems. The processor extension interface allows external hardware to perform special functions and transfer data concurrent with CPU execution of other instructions. Full system integrity is maintained because the 80C286 supervises all data transfers and instruction execution for the processor extension. An 80C286 system which includes the 80287 numeric processor extension (NPX) uses this interface. The 80C286/80287 system has all the instructions and data types of an 80C86 or 80C88 with 8087 numeric processor extension. The 80287 NPX can perform numeric calculations and data transfers concurrently with CPU program execution. Numerics code and data have the same integrity as all other information protected by the 80C286 protection mechanism. The 80C286 can overlap chip select decoding and address propagation during the data transfer for the previous bus operation. This information is latched into the 82C82/83H's by ALE during the middle of a TS cycle. The latched chip select and address information remains stable during the bus operation while the next cycle's address is being decoded and propagated into the system. Decode logic can be implemented with a high speed PROM or PAL. The optional decode logic shown in Figure 30 takes advantage of the overlap between address and data of the 80C286 bus cycle to generate advanced memory and I/O select signals. This minimizes system performance degradation caused by address propagation and decode delays. In addition to selecting memory and I/O, the advanced selects may be used with configurations supporting local and system buses to enable the appropriate bus interface for each bus cycle. The COD/lNTA and M/IO signals are applied to the decode logic to distinguish between interrupt, I/O, code, and data bus cycles. By adding the 82289 bus arbiter chip the 80C286 provides a Multibus system bus interface as shown in Figure 31. The ALE output of the 82C288 for the Multibus bus is connected to its CMDLY input to delay the start of commands one system CLK as required to meet Multibus address and write data setup times. This arrangement will add at least one extra TC state to each bus operation which uses the Multibus. A second 82C288 bus controller and additional latches and transceivers could be added to the local bus of Figure 31. This configuration allows the 80C286 to support an on-board bus for local memory and peripherals, and the Multibus for system bus interfacing. FN2947 Rev.3.00 January 28, 2008 Page 36 of 65 80C286 INTA CYCLE 1 BUS CYCLE TYPE TS TC 1 2 1 2 1 INTA CYCLE 2 TC TC 2 1 TI 2 1 TI TI 2 1 2 1 TS 2 1 TC TC 2 1 2 1 TS 2 1 2 CLK S1 S0 M/IO, COD/INTA (SEE NOTE 21) 80C286 LOCK (SEE NOTE 22) (SEE NOTE 22) DON’T CARE A23 - A0 DON’T CARE BHE D15 - D0 (SEE NOTE 18) PREVIOUS WRITE CYCLE VECTOR (SEE NOTE 19) (SEE NOTE 20) READY NOT READY READY NOT READY READY INTA 82C288 MCE ALE DT/R DEN NOTES: 18. Data is ignored. 19. First INTA cycle should have at least one wait state inserted to meet 82C59A minimum INTA pulse width. 20. Second INTA cycle must have at least one wait state inserted since the CPA will not drive A23-A0, BHE, and LOCK until after the first TC state. The CPU imposed one/clock delay prevents has contention between cascade address buffer being disabled by MCE and address outputs. 21. Without the wait state, the 80C286 address will not be valid for a memory cycle started immediately after the second INTA cycle. The 82C59A also requires one wait state for minimum INTA pulse width. 22. LOCK is active for the first INTA cycle to prevent the 82289 from releasing the bus between INTA cycles in a multi-master system. LOCK is also active for the second INTA cycle. 23. A23-A0 exits three-state OFF during 2 of the second TC in the INTA cycle. FIGURE 29. INTERRUPT ACKNOWLEDGE SEQUENCE FN2947 Rev.3.00 January 28, 2008 Page 37 of 65 FN2947 Rev.3.00 January 28, 2008 SYNC READY ENABLE ASYNC READY ENABLE RESET VCC PROCESSOR EXTENSION (OPTIONAL) 82C284 CLOCK GENERATOR SHDY RESET SRDYEN ARDY ARDYEN X1 S0 RES S1 READY PCLK CLK EFI F/C X2 VCC M/IO MRDC MWTC IORC IOWC INTA ALE MCE DEN DT/R M/IO LOCK CLK COD/INTA READY S1 A23 - A0 S0 NMI BHE HOLD HLDA ERROR INTR BUSY PEACK PEREQ 80C286 CPU D15 - D0 RESET S0 S1 READY CLK CMDLY AEN MB 82C288 BUS CONTROLLER A0 OE 82C86H OR 82C87H TRANSCEIVER T CS INT INTA WR RD SP/EN D0 - D7 82C59A INTERRUPT CONTROLLER CAS0-2 82C82 OR 82C83H LATCH STB OE DECODE (OPTIONAL) DATA BUS IR0 - IR7 CHIP SELECT ADDRESS BUS ADVANCED MEMORY AND I/O CHIP SELECTS MEMORY READ MEMORY WRITE I/O READ I/O WRITE INTERRUPT ACKNOWLEDGE 80C286 FIGURE 30. BASIC 80C286 SYSTEM CONFIGURATION Page 38 of 65 FN2947 Rev.3.00 January 28, 2008 SYNC READY ENABLE ASYNC READY ENABLE RESET VCC S0 S1 READY CLK X1 PROCESSOR EXTENSION (OPTIONAL) 82C284 CLOCK GENERATOR SRDY RESET SRDYEN ARDY ARDYEN PCLK EFI F/C RES X2 VCC VCC RESET M/IO LOCK CLK COD/INTA READY A23 - A0 S1 S0 BHE NMI HOLD HLDA ERROR INTR BUSY PEACK PEREQ 80C286 CPU D15 - D0 MRDC MWTC IORC CMDLY IOWC INTA ALE S0 MCE S1 DEN READY CLK 82C288 DT/R BUS CONTROLLER M/IO AEN SYSB/RESB BCLK INIT RESET CBRQ BREQ ALWAYS BPRO CBQLCK BPRN S0 BUSY S1 CBRQ READY LOCK CLK AEN M/IO 82289 BUS ARBITER MULTIBUS BUS ARBITRATION A0 CS T OE 82C87H TRANSCEIVER 82C59A INTERRUPT CONTROLLER D0 - D7 CAS0-2 INT INTA WR RD SP/EN 82C83H LATCH STB OE DATA BUS IR0 - IR7 CHIP SELECT ADDRESS BUS MEMORY READ MEMORY WRITE I/O READ I/O WRITE INTERRUPT ACKNOWLEDGE 80C286 FIGURE 31. MULTIBUS SYSTEM BUS INTERFACE Page 39 of 65 80C286 / Absolute Maximum Ratings Thermal Information Supply Voltage 8.0V Input, Output or I/O Voltage Applied. . . . . GND -1.0V to VCC +1.0V Storage Temperature Range . . . . . . . . . . . . . . . . . -65oC to +150oC Junction Temperature, PGA . . . . . . . . . . . . . . . . . . . . . . . . . +175oC PLCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150oC Lead Temperature (Soldering, 10s) . . . . . . . . . . . . . . . . . . . +300oC (PLCC - Lead Tips Only) Thermal Resistance (Typical) JA (oC/W) JC (oC/W) PDIP Package . . . . . . . . . . . . . . . . . . . 35 6 CERDIP Package . . . . . . . . . . . . . . . . 33 9 Maximum Package Power Dissipation PGA Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22W PLCC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2W Gate Count . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22,500 CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Operating Conditions Operating Voltage Range 80C286-10, -12 . . . . . . . . . . . . . . . . . . . . . . . . . . . +4.5V to +5.5V 80C286-16, -20, -25 . . . . . . . . . . . . . . . . . . . . . +4.75V to +5.25V Operating Temperature Range I80C286-10, -12, -16, -20 . . . . . . . . . . . . . . . . . . -40oC to +85oC C80C286-12, -16, -20, -25. . . . . . . . . . . . . . . . . . . . 0oC to +70oC DC Electrical Specifications VCC = +5V  10%, TA = 0oC to +70oC (C80C286-12), VCC = +5V  5%, TA = 0oC to +70oC (C80C286-16, -20, -25), VCC = +5V  10%, TA = -40oC to +85oC (I80C286-10, -12), VCC = +5V  5%, TA = -40oC to +85oC (I80C286-16, -20) SYMBOL PARAMETER MIN MAX UNITS VIL Input LOW Voltage -0.5 0.8 V VIH Input HIGH Voltage 2.0 VCC +0.5 V TEST CONDITIONS VILC CLK Input LOW Voltage -0.5 1.0 V VIHC CLK Input HIGH Voltage 3.6 VCC +0.5 V VOL Output LOW Voltage - 0.4 V IOL = 2.0mA VOH Output HIGH Voltage 3.0 VCC -0.4 - V IOH = -2.0mA, IOH = -100A II Input Leakage Current -10 10 A VIN = GND or VCC Pins 29, 31, 57, 59, 61, 63-64 ISH Input Sustaining Current on BUSY and ERROR Pins -30 -500 A VIN = GND (See Note 28) IBHL Input Sustaining Current LOW 38 200 A VIN = 1.0V (See Note 24) IBHH Input Sustaining Current HIGH -50 -400 A VIN = 3.0V (See Note 25) Output Leakage Current -10 10 A VO = GND or VCC Pins 1, 7-8, 10-28, 32-34 - 185 mA 80C286-10 (See Note 27) - 220 mA 80C286-12 (See Note 27) - 260 mA 80C286-16 (See Note 27) - 310 mA 80C286-20 (See Note 27) - 410 mA 80C286-25 (See Note 27) - 5 mA (See Note 26) IO ICCOP ICCSB Active Power Supply Current Standby Power Supply Current Capacitance TA = +25oC, All Measurements Referenced to Device GND SYMBOL PARAMETER TYP UNITS 10 pF CCLK CLK Input Capacitance CIN Other Input Capacitance 10 pF CI/O I/O Capacitance 10 pF TEST CONDITIONS FREQ = 1MHz NOTES: 24. IBHL should be measured after lowering VIN to GND and then raising to 1.0V on the following pins: 36-51, 66, 67. 25. IBHH should be measured after raising VIN to VCC and then lowering to 3.0V on the following pins: 4-6, 36-51, 66-68. 26. ICCSB tested with the clock stopped in phase two of the processor clock cycle. VIN = VCC or GND, VCC = VCC (Max), outputs unloaded. 27. ICCOP measured at 10MHz for the 80C286-10, 12.5MHz for the 80C286-12, 16MHz for the 80C286-16, 20MHz for the 80C286-20, and 25MHz for the 80C286-25. VIN = 2.4V or 0.4V, VCC = VCC (Max), outputs unloaded. 28. ISH should be measured after raising VIN to VCC and then lowering to GND on pins 53 and 54. FN2947 Rev.3.00 January 28, 2008 Page 40 of 65 80C286 AC Electrical Specifications VCC = +5V 10%, TA = 0oC to +70oC (C80C286-12), TA = -40oC to +85oC (I80C286-10, -12) VCC = +5V 5%, TA = 0oC to +70oC (C80C286-16), TA = -40oC to +85oC (I80C286-16) AC Timings are Referenced to 0.8V and 2.0V Points of the Signals as Illustrated in Data Sheet Waveforms, Unless Otherwise Specified 10MHz SYMBOL PARAMETER 12.5MHz 16MHz MIN MAX MIN MAX MIN MAX UNIT TEST CONDITION TIMING REQUIREMENTS 1 System Clock (CLK) Period 50 - 40 - 31 - ns 2 System Clock (CLK) LOW Time 12 - 11 - 7 - ns At 1.0V 3 System Clock (CLK) HIGH Time 16 - 13 - 11 - ns At 3.6V 17 System Clock (CLK) RISE Time - 8 - 8 - 5 ns 1.0V to 3.6V 18 System Clock (CLK) FALL Time - 8 - 8 - 5 ns 3.6V to 1.0V 4 Asynchronous Inputs SETUP Time 20 - 15 - 5 - ns (Note 29) 5 Asynchronous Inputs HOLD Time 20 - 15 - 5 - ns (Note 29) 6 RESET SETUP Time 19 - 10 - 10 - ns 7 RESET HOLD Time 0 - 0 - 0 - ns 8 Read Data SETUP Time 8 - 5 - 5 - ns 9 Read Data HOLD Time 4 - 4 - 3 - ns 10 READY SETUP Time 26 - 20 - 12 - ns 11 READY HOLD Time 25 - 20 - 5 - ns 20 Input RISE/FALL Times - 10 - 8 - 6 ns 0.8V to 2.0V TIMING RESPONSES 12A Status/PEACK Active Delay 1 22 1 21 1 18 ns 1, (Notes 31, 35) 12B Status/PEACK Inactive Delay 1 30 1 24 1 20 ns 1, (Notes 31, 34) 13 Address Valid Delay 1 35 1 32 1 27 ns 1, (Notes 30, 31) 14 Write Data Valid Delay 0 40 0 31 0 28 ns 1, (Notes 30, 31) 15 Address/Status/Data Float Delay 0 47 0 32 0 29 ns 2, (Note 33) 16 HLDA Valid Delay 0 47 0 25 0 25 ns 1, (Notes 31, 36) 19 Address Valid to Status SETUP Time 27 - 22 - 16 - ns 1, (Notes 31, 32) NOTES: 29. Asynchronous inputs are INTR, NMl, HOLD, PEREQ, ERROR, and BUSY. This specification is given only for testing purposes, to assure recognition at a specific CLK edge. 30. Delay from 1.0V on the CLK to 0.8V or 2.0V. 31. Output load: CL = 100pF. 32. Delay measured from address either reaching 0.8V or 2.0V (valid) to status going active reaching 0.8V or status going inactive reaching 2.0V. 33. Delay from 1.0V on the CLK to Float (no current drive) condition. 34. Delay from 1.0V on the CLK to 0.8V for min. (HOLD time) and to 2.0V for max. (inactive delay). 35. Delay from 1.0V on the CLK to 2.0V for min. (HOLD time) and to 0.8V for max. (active delay). 36. Delay from 1.0V on the CLK to 2.0V. AC Test Conditions FN2947 Rev.3.00 January 28, 2008 TEST CONDITION IL (CONSTANT CURRENT SOURCE) CL 1 |2.0mA| 100pF 2 -6mA (VOH to Float) 8mA (VOL to Float) 100pF Page 41 of 65 80C286 AC Electrical Specifications VCC = +5V 5%, TA = 0oC to +70oC (C80C286-20, -25), TA = -40oC to +85oC (l80C286-20) AC Timings are Referenced to the 1.5V Point of the Signals as Illustrated in Data Sheet Waveforms, Unless Otherwise Specified 20MHz SYMBOL PARAMETER 25MHz MIN MAX MIN MAX UNIT TEST CONDITION TIMING REQUIREMENTS 1 System Clock (CLK) Period 25 - 20 - ns 2 System Clock (CLK) LOW Time 6 - 5 - ns At 1.0V 3 System Clock (CLK) HIGH Time 9 - 7 - ns At 3.6V 17 System Clock (CLK) RISE Time - 4 - 4 ns 1.0V to 3.6V 18 System Clock (CLK) FALL Time - 4 - 4 ns 3.6V to 1.0V 4 Asynchronous Inputs SETUP Time 4 - 4 - ns (Note 37) 5 Asynchronous Inputs HOLD Time 4 - 4 - ns (Note 37) 6 RESET SETUP Time 10 - 10 - ns 7 RESET HOLD Time 0 - 0 - ns 8 Read Data SETUP Time 3 - 3 - ns 9 Read Data HOLD Time 2 - 2 - ns 10 READY SETUP Time 10 - 9 - ns 11 READY HOLD Time 3 - 3 - ns 20 Input RISE/FALL Times - 6 - 6 ns 0.8V to 2.0V TIMING RESPONSES 12A Status/PEACK Active Delay 1 15 1 12 ns 1, (Notes 39, 42) 12B Status/PEACK Inactive Delay 1 16 1 13 ns 1, (Notes 39, 42) 13 Address Valid Delay 1 23 1 20 ns 1, (Notes 38, 39) 14 Write Data Valid Delay 0 27 0 24 ns 1, (Notes 38, 39) 15 Address/Status/Data Float Delay 0 25 0 24 ns 2, (Note 41) 16 HLDA Valid Delay 0 20 0 19 ns 1, (Notes 38, 39) 19 Address Valid to Status SETUP Time 9 - 12 - ns 1, (Notes 39, 40) NOTES: 37. Asynchronous inputs are INTR, NMl, HOLD, PEREQ, ERROR, and BUSY. This specification is given only for testing purposes, to assure recognition at a specific CLK edge. 38. Delay from 1.0V on the CLK to 1.5V. 39. Output load: CL = 100pF. 40. Delay measured from address reaching 1.5V to status reaching 1.5V. 41. Delay from 1.0V on the CLK to Float (no current drive) condition. 42. Delay from 1.0V on the CLK to 1.5V. AC Test Conditions FN2947 Rev.3.00 January 28, 2008 TEST CONDITION IL (CONSTANT CURRENT SOURCE) CL 1 |2.0mA| 100pF 2 -6mA (VOH to Float) 8mA (VOL to Float) 100pF Page 42 of 65 80C286 AC Specifications (Continued) C80C86-12, -16 I80C286-10, -12, -16 AC DRIVE AND MEASURE POINTS - CLK INPUT 4.0V 3.6V 3.6V CLK INPUT 1.0V 1.0V 0.45V 4.0V 3.6V 3.6V CLK INPUT 1.0V 1.0V 0.45V tSETUP tHOLD 2.4V OTHER DEVICE INPUT 2.0V 2.0V 0.8V 0.8V 0.4V tDELAY (MAX) tDELAY (MAX) 2.0V DEVICE OUTPUT 0.8V NOTE: For AC testing, input rise and fall times are driven at 1ns per volt. FIGURE 32. FN2947 Rev.3.00 January 28, 2008 Page 43 of 65 80C286 AC Specifications (Continued) C80C286-20, -25 I80C286-20 AC DRIVE AND MEASURE POINTS - CLK INPUT 4.0V 3.6V 3.6V CLK INPUT 1.0V 1.0V 0.45V 4.0V 3.6V 3.6V CLK INPUT 1.0V 1.0V 0.45V tSETUP tHOLD 2.4V OTHER DEVICE INPUT 2.0V 2.0V 0.8V 0.8V 0.4V tDELAY DEVICE OUTPUT 1.5V NOTE: Typical Output Rise/Fall Time is 6ns. For AC testing, input rise and fall times are driven at 1ns per volt. FIGURE 33. FN2947 Rev.3.00 January 28, 2008 Page 44 of 65 80C286 AC Electrical Specifications 82C284 and 82C288 Timing Specifications are given for reference only and no guarantee is implied. 82C284 Timing 10MHz SYMBOL PARAMETER 12.5MHz 16MHz MIN MAX MIN MAX MIN MAX UNIT TEST CONDITION TIMING REQUIREMENTS 11 SRDY/SRDYEN Setup Time 15 - 15 - 10 - ns 12 SRDY/SRDYEN Hold Time 2 - 2 - 1 - ns 13 ARDY/ARDYEN Setup Time 5 - 5 - 3 - ns (Note 43) 14 ARDY/ARDYEN Hold Time 30 - 25 - 20 - ns (Note 43) 0 20 0 16 0 15 ns CL = 75pF, IOL = 5mA, IOH = 1mA TIMING RESPONSES 19 PCLK Delay NOTE: 43. These times are given for testing purposes to ensure a predetermined action. 82C288 Timing 10MHz SYMBOL PARAMETER 12.5MHz 16MHz MIN MAX MIN MAX MIN MAX UNIT TEST CONDITION TIMING REQUIREMENTS 12 CMDLY Setup Time 15 - 15 - 10 - ns 13 CMDLY Hold Time 1 - 1 - 0 - ns TIMING RESPONSES 16 ALE Active Delay 1 16 1 16 1 12 ns 17 ALE Inactive Delay - 19 - 19 - 15 ns 19 DT/R Read Active Delay - 23 - 23 - 18 ns CL = 150pF 20 DEN Read Active Delay - 21 - 21 - 16 ns IOL = 16mA Max 21 DEN Read Inactive Delay 3 23 3 21 5 14 ns IOL = 1mA Max 22 DT/R Read Inactive Delay 5 24 5 18 5 14 ns 23 DEN Write Active Delay - 23 - 23 - 17 ns 24 DEN Write Inactive Delay 3 23 3 23 3 15 ns 29 Command Active Delay from CLK 3 21 3 21 3 15 ns CL = 300pF 30 Command Inactive Delay from CLK 3 20 3 20 3 15 ns IOL = 32mA Max NOTE: 44. These times are given for testing purposes to ensure a predetermined action. FN2947 Rev.3.00 January 28, 2008 Page 45 of 65 80C286 Waveforms BUS CYCLE TYPE TI 3 VOH READ CYCLE WRITE CYCLE ILLUSTRATED WITH ZERO ILLUSTRATED WITH ONE WAIT STATES WAIT STATE TS TC TS 1 2 2 1 2 1 2 READ (TS OR TS) TC 1 TC 2 1 2 1 CLK VOL 2 12B 12A S1  S0 19 19 13 80C286 13 A23 - A0 M/IO, COD, INTA VALID ADDRESS 13 13 VALID CONTROL VALID CONTROL BHE, LOCK VALID IF TS VALID ADDRESS 9 14 8 15 VALID WRITE DATA D15 - D0 VALID READ DATA 11 11 10 10 READY 12 11 SRDY + SRDYEN 82C284 19 14 13 ARDY + ARDYEN 19 19 16 17 20 PLCK ALE 13 12 13 12 13 12 CMDLY 82C288 29 MWTC (SEE NOTE 1) 30 29 30 MRDC 19 DT/R 22 20 21 24 23 DEN FIGURE 34. MAJOR CYCLE TIMING NOTE: The modified timing is due to the CMDLY signal being active. FN2947 Rev.3.00 January 28, 2008 Page 46 of 65 80C286 Waveforms (Continued) VCH BUS CYCLE TYPE VCH TX 1 2 19 TX 1 1 2 CLK CLK VCL 2 VCL 19 PCLK (SEE NOTE 47) (SEE NOTE 47) 7 6 RESET 5 4 VCH INTR, NMI HOLD, PEREQ (SEE NOTE 45) TX 2 1 1 CLK 4 5 VCL ERROR, BUSY (SEE NOTE 46) (SEE NOTE 47) 7 6 RESET FIGURE 35. 80C286 ASYNCHRONOUS INPUT SIGNAL TIMING NOTES: 45. PCLK indicates which processor cycle phase will occur on the next CLK, PCLK may not indicate the correct phase until the first cycle is performed. FIGURE 36. 80C286 RESET INPUT TIMING AND SUBSEQUENT PROCESSOR CYCLE PHASE NOTE: 47. When RESET meets the setup time shown, the next CLK will start or repeat 1 of a processor cycle. 46. These inputs are asynchronous. The setup and hold times shown assure recognition for testing purposes. FN2947 Rev.3.00 January 28, 2008 Page 47 of 65 80C286 Waveforms (Continued) BUS CYCLE TYPE VCH TS OR TI TH 2 1 1 2 1 TI 2 1 TH 2 CLK VCL HLDA 16 16 (SEE NOTE 51) 12A (SEE NOTE 50) 15 S1  S0 IF TS 12B 80C286 (SEE NOTE 50) 15 CLK BHE, LOCK A23 - A0, M/IO, COD/INTA IF NPX TRANSFER (SEE NOTE 48) 15 13 (SEE NOTE 52) VALID (SEE NOTE 49) 14 D15 - D0 15 (SEE NOTE 53) 80C284 VALID IF WRITE PCLK FIGURE 37. EXITING AND ENTERING HOLD NOTES: 48. These signals may not be driven by the 80C286 during the time shown. The worst case in terms of latest float time is shown. 49. The data bus will be driven as shown if the cycle before TI in the diagram was a write TC. 50. The 80C286 puts its status pins in a high impedance logic one state during TH. 51. For HOLD request set up to HLDA, refer to Figure 29. 52. BHE and LOCK are driven at this time but will not become valid until TS. 53. The data bus will remain in a high impedance state if a read cycle is performed. © Copyright Intersil Americas LLC 2003-2008. All Rights Reserved. All trademarks and registered trademarks are the property of their respective owners. For additional products, see www.intersil.com/en/products.html Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted in the quality certifications found at www.intersil.com/en/support/qualandreliability.html Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see www.intersil.com FN2947 Rev.3.00 January 28, 2008 Page 48 of 65 80C286 Waveforms (Continued) BUS CYCLE TYPE VCH TI 2 1 TS 2 1 TC 2 TS 1 2 1 TC 2 1 TI CLK VCL I/O READ IF PROC. EXT. TO MEMORY MEMORY READ IF MEMORY TO PROC. EXT. MEMORY WRITE IF PROC. EXT. TO MEMORY I/O WRITE IF MEMORY TO PROC. EXT. S1  S0 MEMORY ADDRESS IF PROC. EXT. TO MEMORY TRANSFER I/O PORT ADDRESS 00FA(H) IF MEMORY TO PROC. EXT. TRANSFER A23 - A0 M/IO, COD INTA 12A PEACK I/O PORT ADDRESS 00FA(H) IF PROC. EXT. TO MEMORY TRANSFER MEMORY ADDRESS IF MEMORY TO PROC. EXT. TRANSFER 12B (SEE NOTE 54) (SEE NOTE 55) 4 5 PEREQ ASSUMING WORD-ALIGNED MEMORY OPERAND. IF ODD ALIGNED, 80C286 TRANSFERS TO/FROM MEMORY BYTE-AT-A-TIME WITH TWO MEMORY CYCLES. FIGURE 38. 80C286 PEREQ/PEACK TIMING FOR ONE TRANSFER ONLY NOTES: 54. PEACK always goes active during the first bus operation of a processor extension data operand transfer sequence. The first bus operation will be either a memory read at operand address or I/O read at port address 00FA(H). 55. To prevent a second processor extension data operand transfer, the worst case maximum time (Shown above) is 3 x 1 - 12AMAX - 4 MIN. The actual configuration dependent, maximum time is: 3 x 1 - 12AMAX - 4 MIN + N x 2 x 1 . N is the number of extra TC states added to either the first or second bus operation of the processor extension data operand transfer sequence. BUS CYCLE TYPE VCH TX 2 2 1 19 (SEE NOTE 56) 1 TX 2 1 TX 2 1 TI 2 CLK VCL RESET S1  S0 PEACK A23 - A0 BHE 7 AT LEAST 16 CLK PERIODS 6 (SEE NOTE 57) 12B UNKNOWN 13 UNKNOWN 13 M/IO COD/INTA UNKNOWN 13 LOCK UNKNOWN 15 (SEE NOTE 58) DATA 16 HLDA UNKNOWN FIGURE 39. INITIAL 80C286 PIN STATE DURING RESET NOTES: 56. Setup time for RESET  may be violated with the consideration that 1 of the processor clock may begin one system CLK period later. 57. Setup and hold times for RESET  must be met for proper operation, but RESET  may occur during 1 or 2. 58. The data bus is only guaranteed to be in a high impedance state at the time shown. FN2947 Rev.3.00 January 28, 2008 Page 49 of 65 80C286 Waveforms (Continued) BYTE 1 BYTE 3 BYTE 4 BYTE 5 BYTE 6 LOW DISP/DATA HIGH DISP/DATA LOW DATA HIGH DATA BYTE 2 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 OPCODE d w MOD REG R/M REGISTER OPERAND REGISTERS TO USE IN OFFSET CALCULATION REGISTER OPERAND/EXTENSION OF OPCODE REGISTER MODE/MEMORY MODE WITH DISPLACEMENT LENGTH WORD/BYTE OPERATION DIRECTION IS TO REGISTER DIRECTION IS FROM REGISTER OPERATION (INSTRUCTION) CODE FIGURE 40A. SHORT OPCODE FORMAT EXAMPLE BYTE 1 BYTE 2 BYTE 3 BYTE 4 BYTE 5 LOW DISP HIGH DISP 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 LONG OPCODE MOD REG R/M FIGURE 40B. LONG OPCODE FORMAT EXAMPLE FIGURE 40. 80C286 INSTRUCTION FORMAT EXAMPLES 80C286 Instruction Set Summary Instruction Timing Notes The instruction clock counts listed below establish the maximum execution rate of the 80C286. With no delays in bus cycles, the actual clock count of an 80C286 program will average 5% more than the calculated clock count, due to instruction sequences which execute faster than they can be fetched from memory. Greater refers to more positive signed values. To calculate elapsed times for instruction sequences, multiply the sum of all instruction clock counts, as listed in the table below, by the processor clock period. An 12.5MHz processor clock has a clock period of 80 nanoseconds and requires an 80C286 system clock (CLK input) of 25MHz. if s = 0, then 16-bit immediate data form the operand Instruction Clock Count Assumptions z used for string primitives for comparison with ZF FLAG Less refers to less positive (more negative) signed values if d = 1, then “to” register; if d = 0 then “from” register if w = 1, then word instruction; if w = 0, then byte instruction if s = 1, then an immediate data byte is sign-extended to form the 16-bit operand x don’t care 1. The instruction has been perfected, decoded and is ready for execution. Control transfer instruction clock counts include all time required to fetch, decode, and prepare the next instruction for execution. If two clock counts are given, the smaller refers to a register operand and the larger refers to a memory operand 2. Bus cycles do not require wait states. n = number of times repeated 3. There are no processor extension data transfer or local bus HOLD requests. m = number of bytes of code in next instruction 4. No exceptions occur during instruction execution. Instruction Set Summary Notes Addressing displacements selected by the MOD field are not shown. If necessary they appear after the instruction fields shown. * = add one clock if offset calculation requires summing 3 elements Level (L) - Lexical nesting level of the procedure The following comments describe possible exceptions, side effects and allowed usage for instructions in both operating modes of the 80C286. Above/below refers to unsigned value. FN2947 Rev.3.00 January 28, 2008 Page 50 of 65 80C286 Real Address Mode Only 1. This is a protected mode instruction. Attempted execution in real address mode will result in an undefined opcode exception (6). 2. A segment overrun exception (13) will occur if a word operand references at offset FFFF(H) is attempted. 3. This instruction may be executed in real address mode to initialize the CPU for protected mode. 4. The IOPL and NT fields will remain 0. 5. Processor extension segment overrun interrupt (9) will occur if the operand exceeds the segment limit. Either Mode 6. An exception may occur, depending on the value of the operand. 7. LOCK is automatically asserted regardless of the presence or absence of the LOCK instruction prefix. 8. LOCK does not remain active between all operand transfers. (11). If the SS register is the destination and a segment not-present violation occurs, a stack exception (12) occurs. 11. All segment descriptor accesses in the GDT or LDT made by this instruction will automatically assert LOCK to maintain descriptor integrity in multiprocessor systems. 12. JMP, CALL, INT, RET, IRET instructions referring to another code segment will cause a general protection exception (13) if any privilege rule is violated. 13. A general protection exception (13) occurs if CPL 0. 14. A general protection exception (13) occurs if CPL > IOPL. 15. The IF field of the flag word is not updated if CPL > IOPL. The IOPL field is updated only if CPL = 0. 16. Any violation of privilege rules as applied to the selector operand does not cause a protection exception; rather, the instruction does not return a result and the zero flag is cleared. 9. A general protection exception (13) will occur if the memory operand cannot be used due to either a segment limit or access rights violation. If a stack segment limit is violated, a stack segment overrun exception (12) occurs. 17. If the starting address of the memory operand violates a segment limit, or an invalid access is attempted, a general protection exception (13) will occur before the ESC instruction is executed. A stack segment overrun exception (12) will occur if the stack limit is violated by the operand’s starting address. If a segment limit is violated during an attempted data transfer then a processor extension segment overrun exception (9) occurs. 10. For segment load operations, the CPL, RPL and DPL must agree with privilege rules to avoid an exception. The segment must be present to avoid a not-present exception 18. The destination of an INT, JMP, CALL, RET or IRET instruction must be in the defined limit of a code segment or a general protection exception (13) will occur. Protected Virtual Address Mode Only 80C286 Instruction Set Summary FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE PROTECTED VIRTUAL ADDRESS MODE DATA TRANSFER MOV = Move Register to Register/Mem- 1000100w mod ory r/m reg 2, 3 2, 3 (Note 59) (Note 59) 2 9 Register/Memory to Regis- 1000101w mod ter r/m reg 2, 5 2, 5 (Note 59) (Note 59) 2 9 2, 3 2, 3 (Note 59) (Note 59) 2 9 Immediate to Register/Mem- 1100011w mod 000 data ory r/m data if w=1 Immediate to Register 1011w reg data data if w = 1 2 2 Memory to Accumulator 1010000w addr-low addr-high 5 5 2 9 Accumulator to Memory 1010001w addr-low addr-high 3 3 2 9 FN2947 Rev.3.00 January 28, 2008 Page 51 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE PROTECTED VIRTUAL ADDRESS MODE Register/Memory to Seg- 10001110 mod 0 reg ment Register r/m 2, 5 17, 19 (Note 59) (Note 59) 2 9, 10, 11 Segment Register to Regis- 10001100 mod 0 reg ter/Memory r/m 2, 3 2, 3 (Note 59) (Note 59) 2 9 5 5 (Note 59) (Note 59) 2 9 PUSH = Push Memory 11111111 mod r/m 110 Register 01010 reg 3 3 2 9 Segment Register 000 110 3 3 2 9 Immediate 011010s0 data 3 3 2 9 PUSHA = Push All 01100000 17 17 2 9 5 5 (Note 59) (Note 59) 2 9 5 5 2 9 5 20 2 9, 10, 11 19 19 2 9 2, 7 7, 9 reg data if s = 0 POP = Pop Memory 10001111 mod r/m Register 01011 reg Segment Register 000 111 POPA = Pop All 01100001 000 reg (reg  01) XCHG = Exchange Register/Memory with Reg- 1000011w mod ister r/m Register with Accumulator reg 3, 5 3, 5 (Note 59) (Note 59) 10010 reg 3 3 Fixed Port 1110010w port 5 5 14 Variable Port 1110110w 5 5 14 Fixed Port 1110011w port 3 3 14 Variable Port 1110111w 3 3 14 XLAT = Translate Byte to 11010111 AL 5 5 9 IN = Input From OUT = Output To FN2947 Rev.3.00 January 28, 2008 Page 52 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE PROTECTED VIRTUAL ADDRESS MODE LEA = Load EA to Register 10001101 mod r/m reg 3 3 (Note 59) (Note 59) LDS = Load Pointer to DS 11000101 mod r/m reg (mod  11) 7 21 (Note 59) (Note 59) 2 9, 10, 11 LES = Load Pointer to ES 11000100 mod r/m reg (mod  1) 7 21 (Note 59) (Note 59) 2 9, 10, 11 LAHF Load AH with Flags 10011111 2 2 SAHF = Store AH into Flags 10011110 2 2 PUSHF = Push Flags 10011100 3 3 2 9 POPF = Pop Flags 10011101 5 5 2, 4 9, 15 2, 7 2, 7 (Note 59) (Note 59) 2 9 3, 7 3, 7 (Note 59) (Note 59) 2 9 2, 7 2, 7 (Note 59) (Note 59) 2 9 3, 7 3, 7 (Note 59) (Note 59) 2 9 2 9 2 9 ARlTHMETlC ADD = Add Reg/Memory with Register 000000dw mod to r/m Either reg Immediate ter/Memory 000 data to Regis- 100000sw mod r/m Immediate to Accumulator 0000010w data data if sw = 01 data if w = 1 3 3 ADC = Add with Carry Reg/Memory with Register 000100dw mod to r/m Either reg Immediate ter/Memory 010 data to Regis- 100000sw mod r/m Immediate to Accumulator 0001010w data data if w = 1 data if sw = 01 3 3 INC = Increment Register/Memory 1111111w mod r/m Register 01000 reg 000 2, 7 2, 7 (Note 59) (Note 59) 2 2 SUB = Subtract Reg/Memory and Register 001010dw mod to r/m Either FN2947 Rev.3.00 January 28, 2008 reg 2, 7 2, 7 (Note 59) (Note 59) Page 53 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION Immediate ter/Memory FORMAT from Regis- 100000sw mod r/m 101 data Immediate from Accumula- 0010110w data tor data if sw = 01 data if w = 1 CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE 2 9 2, 7 2, 7 (Note 59) (Note 59) 2 9 3, 7 3, 7 (Note 59) (Note 59) 2 9 2 9 PROTECTED VIRTUAL ADDRESS MODE 3, 7 3, 7 (Note 59) (Note 59) 3 3 SBB = Subtract with Borrow Reg/Memory and Register 000110dw mod to r/m Either reg Immediate ter/Memory 011 data from Regis- 100000sw mod r/m Immediate from Accumula- 0001110w data tor data if sw = 01 data if w = 1 3 3 DEC = Decrement Register/Memory 1111111w mod r/m Register 01001 reg 001 2, 7 2, 7 (Note 59) (Note 59) 2 2 CMP = Compare Register/Memory with Reg- 0011101w mod ister r/m reg 2, 6 2, 6 (Note 59) (Note 59) 2 9 Register with ter/Memory Regis- 0011100w mod r/m reg 2, 7 2, 7 (Note 59) (Note 59) 2 9 Immediate ter/Memory Regis- 100000sw mod r/m 111 data 3, 6 3, 6 (Note 59) (Note 59) 2 9 2 7 with Immediate with Accumula- 0011110w data tor 3 3 2 7 (Note 59) AAA = ASCII Adjust for Add 00110111 3 3 DAA = Decimal Adjust for 00100111 Add 3 3 AAS = ASCII Adjust for 00111111 Subtract 3 3 DAS = Decimal Adlust for 00101111 Subtract 3 3 NEG = Change Sign 1111011w mod r/m MUL = Multiply (Unsigned) 1111011w mod r/m FN2947 Rev.3.00 January 28, 2008 data if w = 1 data if sw = 01 011 100 Page 54 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE Register - Byte 13 13 Register - Word 21 21 Memory - Byte 16 16 (Note 59) (Note 59) 2 9 Memory - Word 24 24 (Note 59) (Note 59) 2 9 IMUL = Integer Multiply (Signed) 1111011w mod r/m 101 Register - Byte 13 13 Register - Word 21 21 Memory - Byte 16 16 (Note 59) (Note 59) 2 9 Memory - Word 24 24 (Note 59) (Note 59) 2 9 data if s = 21, 24 21, 24 0 (Note 59) (Note 59) 2 9 IMUL = Interger Immediate 011010s1 mod Multiply (Signed) r/m reg data DIV = Divide (Unsigned) 110 1111011w mod r/m Register - Byte 14 14 6 6 Register - Word 22 22 6 6 Memory - Byte 17 17 (Note 59) (Note 59) 2, 6 6, 9 Memory - Word 25 25 (Note 59) (Note 59) 2, 6 6, 9 Register - Byte 17 17 6 6 Register - Word 25 25 6 6 Memory - Byte 20 20 (Note 59) (Note 59) 2, 6 6, 9 Memory - Word 28 28 (Note 59) (Note 59) 2, 6 6, 9 AAM = ASCII Adjust for 11010100 00001010 Multiply 16 IDIV = (Signed) Integer FN2947 Rev.3.00 January 28, 2008 Divide 1111011w mod r/m 111 16 Page 55 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE AAD = ASCII Adjust for 11010101 00001010 Divide 14 14 CBW = Convert Byte to 10011000 Word 2 2 CWD = Convert Word to 10011001 Double Word 2 2 LOGIC Shift/Rotate Instructions Register/Memory by 1 1101000w mod r/m TTT 2, 7 2, 7 (Note 59) (Note 59) 2 9 Register/Memory by CL 1101001w mod r/m TTT 5+n, 8+n 5+n, 8+n (Note 59) (Note 59) 2 9 TTT count 5+n, 8+n 5+n, 8+n (Note 59) (Note 59) 2 9 2, 7 2, 7 (Note 59) (Note 59) 2 9 data if w = 3, 7 3, 7 1 (Note 59) (Note 59) 2 9 2 9 Register/Memory by Count 1100000 mod r/m TTT Instruction 000 ROL 001 ROR 010 RCL 011 RCR 100 SHL/SAL 101 SHR 111 SAR AND = And Reg/Memory and Register 001000dw mod to r/m Either reg Immediate ter/Memory 100 data to Regis- 1000000w mod r/m Immediate to Accumulator 0010010w data data if w = 1 3 3 TEST = And Function to Flags, No Result Register/Memory and Reg- 1000010w mod ister r/m FN2947 Rev.3.00 January 28, 2008 reg 2, 6 2, 6 (Note 59) (Note 59) Page 56 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE 2 9 2, 7 2, 7 (Note 59) (Note 59) 2 9 data if w = 3, 7 3, 7 1 (Note 59) (Note 59) 2 9 2, 7 2, 7 (Note 59) (Note 59) 2 9 data if w = 3, 7 3, 7 1 (Note 59) (Note 59) 2 9 2, 7 2, 7 (Note 59) (Note 59) 2 9 1010010w 5 5 2 9 Compare 1010011w 8 8 2 9 1010111w 7 7 2 9 LODS = Load Byte/Word to 1010110w AL/AX 5 5 2 9 STOS = Store Byte/Word 1010101w from AL/A 3 3 2 9 INS = Input Byte/Word from 0110110w DX Port 5 5 2 9, 14 OUTS = Output Byte/Word 0110111w to DX Port 5 5 2 9, 14 Immediate Data and Regis- 1111011w mod ter/Memory r/m 000 data Immediate Data and Accu- 1010100w data mulator data if w = 1 PROTECTED VIRTUAL ADDRESS MODE data if w = 3, 6 3, 6 1 (Note 59) (Note 59) 3 3 OR = Or Reg/Memory and Register 000010dw mod to r/m Either reg Immediate ter/Memory 001 data to Regis- 1000000w mod r/m Immediate to Accumulator 0000110w data data if w = 1 3 3 XOR = Exclusive or Reg/Memory and Register 001100dw mod r/m to Either reg Immediate ter/Memory reg data to Regis- 1000000w mod r/m Immediate to Accumulator NOT = Invert ter/Memory 0011010w data Regis- 1111011w mod r/m data if w = 1 010 3 3 STRING MANIPULATION MOVS = Move Byte/Word CMPS = Byte/Word SCAS = Scan Byte/Word FN2947 Rev.3.00 January 28, 2008 Page 57 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE Repeated by Count in CX MOVS = Move String 11110011 1010010w 5 + 4n 5 + 4n 2 9 CMPS = Compare String 1111001z 1010011w 5 + 9n 5 + 9n 2, 8 8, 9 SCAS = Scan String 1111001z 1010111w 5 + 8n 5 + 8n 2, 8 8, 9 LODS = Load String 11110011 1010110w 5 + 4n 5 + 4n 2, 8 8, 9 STOS = Store String 11110011 1010101w 4 + 3n 4 + 3n 2, 8 8, 9 INS = Input String 11110011 0110110w 5 + 4n 5 + 4n 2 9, 14 OUTS = Output String 11110011 0110111w 5 + 4n 5 + 4n 2 9, 14 7+m 7+m 2 18 7 + m, 7 + m, 11 + m 11 + m (Note 59) (Note 59) 2, 8 8, 9, 18 13 + m 2 11, 12,18 CONTROL TRANSFER CALL = Call Direct Within Segment Register/Memory Within Segment 11101000 disp-low Indirect 11111111 mod r/m Direct Intersegment Protected Mode Only (Direct Intersegment) disp-high 010 10011010 Segment Offset 26 + m Segment Selector Via Call Gate to Same Privilege Level 41 + m 8, 11, 12, 18 Via Call Gate to Different Privilege Level, No Parameters 82 + m 8, 11, 12, 18 Via Call Gate to Different Privilege Level, X Parameters 86 + 4x + m 8, 11, 12, 18 Via TSS 177 + m 8, 11, 12, 18 Via Task Gate 182 + m 8, 11, 12, 18 Indirect Intersegment 11111111 mod r/m 011 mod  11 16 + m 29 + m (Note 59) (Note 59) 2 8, 9, 11, 12, 18 Protected Mode Only (Indirect Intersegment) Via Call Gate to Same Privilege Level FN2947 Rev.3.00 January 28, 2008 44 + m (Note 59) 8, 9, 11, 12, 18 Page 58 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE PROTECTED VIRTUAL ADDRESS MODE Via Call Gate to Different Privilege Level, No Parameters 83 + m (Note 59) 8, 9, 11, 12, 18 Via Call Gate to Different Privilege Level, X Parameters 90 + 4x + m (Note 59) 8, 9, 11, 12, 18 Via TSS 180 + m (Note 59) 8, 9, 11, 12, 18 185 + m (Note 59) 8, 9, 11, 12, 18 7+m 7+m 18 7+m 7+m 18 Protected Mode Only (Indirect Intersegment) (Continued) Via Task Gate JMP = Unconditional Jump Short/Long 11101011 disp-low Direct Within Segment 11101001 disp-low Register/Memory Indirect Within Segment 11111111 mod r/m Direct Intersegment 11101010 Segment Offset disp-high 100 7 + m, 7 + m, 11 + m 11 + m (Note 59) (Note 59) 9, 18 23 + m 11, 12, 18 Via Call Gate to Same Privilege Level 38 + m 8, 11,12,18 Via TSS 175 + m 8, 11,12,18 Via Task Gate 180 + m 8, 11,12,18 Protected Mode Only (Direct Intersegment) Indirect Intersegment 11 + m 2 Segment Selector 11111111 mod r/m 101 mod  11 15 + m 26 + m (Note 59) (Note 59) 2 8, 9, 11, 12, 18 Protected Mode Only (Indirect Intersegment) Via Call Gate to Same Privilege Level 41 + m (Note 59) 8, 9, 11, 12, 18 Via TSS 178 + m (Note 59) 8, 9, 11, 12, 18 Via Task Gate 183 + m (Note 59) 8, 9, 11, 12, 18 RET = Return from CALL Within Segment FN2947 Rev.3.00 January 28, 2008 11000011 11 + m 11 + m 2 8, 9, 18 Page 59 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT Within Segment Adding Immediate to SP 11000010 data-low Intersegment 11001011 Intersegment Adding Immediate to SP 11001010 data-low data-high data-high CLOCK COUNT COMMENTS REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE 11 + m 11 + m 2 8, 9, 18 15 + m 25 + m 2 8, 9, 11, 12, 18 2 8, 9, 11, 12, 18 15 + m Protected Mode Only (RET) To Different Level Privilege 55 + m 9, 11, 12, 18 JE/JZ = Jump on Equal 01110100 disp Zero 7 + m or 7 + m or 3 3 18 JL/JNGE = Jump on 01111100 disp Less/Not Greater or Equal 7 + m or 7 + m or 3 3 18 JLE/JNG = Jump on Less 01111110 disp or Equal/not Greater 7 + m or 7 + m or 3 3 18 JB/JNAE = Jump on 01110010 disp Below/Not Above or Equal 7 + m or 7 + m or 3 3 18 JBE/JNA = Jump on Below 01110110 disp or Equal/Not Above 7 + m or 7 + m or 3 3 18 JP/JPE = Jump on Par- 01111010 disp ity/Parity Even 7 + m or 7 + m or 3 3 18 JO = Jump on Overflow 01110000 disp 7 + m or 7 + m or 3 3 18 JS = Jump on Sign 01111000 disp 7 + m or 7 + m or 3 3 18 JNE/JNZ = Jump on Not 01110101 disp Equal/Not Zero 7 + m or 7 + m or 3 3 18 JNL/JGE = Jump on Not 01111101 disp Less/Greater or Equal 7 + m or 7 + m or 3 3 18 JNLE/JG = Jump on Not 01111111 disp Less or Equal/Greater 7 + m or 7 + m or 3 3 18 JNB/JAE = Jump on Not 01110011 disp Below/Above or Equal 7 + m or 7 + m or 3 3 18 JNBE/JA = Jump on Not 01110111 disp Below or Equal/Above 7 + m or 7 + m or 3 3 18 JNP/JPO = Jump on Not 01111011 disp Par/Par Odd 7 + m or 7 + m or 3 3 18 FN2947 Rev.3.00 January 28, 2008 Page 60 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE PROTECTED VIRTUAL ADDRESS MODE JNO = Jump on Not Over- 01110001 disp flow 7 + m or 7 + m or 3 3 18 JNS = Jump on Not Sign 01111001 disp 7 + m or 7 + m or 3 3 18 LOOP Loop CX Times 11100010 disp 8 + m or 8 + m or 4 4 18 Loop 11100001 disp 8 + m or 8 + m or 4 4 18 LOOPNZ/LOOPNE = Loop 11100000 disp While Not Zero/Equal 8 + m or 8 + m or 4 4 18 JCXZ = Jump on CX Zero 8 + m or 8 + m or 4 4 18 LOOPZ/LOOPE = While Zero/Equal 11100011 disp ENTER = Enter Procedure 11001000 data-low data-high L 2, 8 8, 9 L=0 11 11 2, 8 8, 9 L=1 15 15 2, 8 8, 9 L>1 16 + 4(L - 16 + 4(L - 1) 2, 8 1) 8, 9 LEAVE = Leave Procedure 11001001 5 5 INT = Interrupt Type Specified 11001101 type 23 + m 2, 7, 8 Type 3 11001100 23 + m 2, 7, 8 24 + m or (3 if no 3 interrupt) (3 if no interrupt) 2, 6, 8 lNTO = Interrupt on Over- 11001110 flow Protected Mode Only Via Interrupt or Trap Gate to Same Privilege Level 40 + m 7, 8, 11, 12, 18 Via Interrupt or Trap Gate to Fit Different Pnvilege Level 78 + m 7, 8, 11, 12, 18 Via Task Gate 167 + m 7, 8, 11, 12, 18 IRET Interrupt Return FN2947 Rev.3.00 January 28, 2008 11001111 17 + m 31 + m 2, 4 8, 9, 11, 12, 15, 18 Page 61 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE PROTECTED VIRTUAL ADDRESS MODE Protected Mode Only To Different Level Privilege To Different Task (NT = 1) BOUND = Detect Value Out 01100010 mod of Range r/m reg 55 + m 8, 9, 11, 12, 15, 18 169 + m 8, 9, 11, 12, 18 13 13 2, 6 (Note 59) (Use INT clock count if exception 5) (Note 59) 6, 8, 9, 11, 12, 18 PROCESSOR CONTROL CLC = Clear Carry 11111000 2 2 CMC = Complement Carry 11110101 2 2 STC = Set Carry 11111001 2 2 CLD = Clear Direction 11111100 2 2 STD = Set Direction 11111101 2 2 CLI = Clear Interrupt 11111010 3 3 14 STI = Set Interrupt 11111011 2 2 14 HLT = Halt 11110100 2 2 13 WAIT = Wait 10011011 3 3 LOCK = Bus Lock Prefix 11110000 0 0 CTS = Clear Task Switched 00001111 00000110 Flag 2 2 ESC = Processor Extension 11011TTT mod Escape r/m 9-20 9-20 (Note 59) (Note 59) LLL 14 3 13 5, 8 8, 17 (TTT LLL Are Opcode to Processor Extension) SEG = Segment Override 001 Prefix 110 reg 0 0 PROTECTION CONTROL LGDT = Load Global 00001111 00000001 mod Descriptor Table Register r/m 010 11 11 (Note 59) (Note 59) 2, 3 9, 13 SGDT = Store Global 00001111 00000001 mod Desceptor Table Register r/m 000 11 11 (Note 59) (Note 59) 2, 3 9 FN2947 Rev.3.00 January 28, 2008 Page 62 of 65 80C286 80C286 Instruction Set Summary (Continued) FUNCTION FORMAT CLOCK COUNT COMMENTS REAL ADDRES S MODE REAL ADDRES S MODE PROTECTED VIRTUAL ADDRESS MODE PROTECTED VIRTUAL ADDRESS MODE LIDT = Load Interrupt 00001111 00000001 mod Descriptor Table Register r/m 011 12 12 (Note 59) (Note 59) 2, 3 9, 13 SIDT = Store Interrupt 00001111 00000001 mod Descriptor Table Register r/m 001 12 12 (Note 59) (Note 59) 2, 3 9 LLDT = Load Local 00001111 00000000 mod Descriptor Table Register r/m From Register Memory 010 17, 19 (Note 59) 1 9, 11, 13 SLDT = Store Local 00001111 00000000 mod Descriptor Table Register r/m To Register/Memory 000 2, 3 (Note 59) 1 9 LTR = LTR = Local Task 00001111 00000000 mod Register From Regisr/m ter/Memory 011 17, 19 (Note 59) 1 9, 11, 13 STR = Store Task Register 00001111 00000000 mod To Register Memory r/m 001 2, 3 (Note 59) 1 9 LMSW = Load Machine 00001111 00000001 mod r/m Status Word From Register/Memory 110 3, 6 3, 6 (Note 59) (Note 59) 2, 3 9, 13 SMSW = Store Machine 00001111 00000001 mod Status Word r/m 100 2, 3 2, 3 (Note 59) (Note 59) 2, 3 9 LAR = Load Access Rights 00001111 00000010 mod From Register/Memory r/m reg 14, 16 (Note 59) 1 9, 11, 16 LSL = Load Segment Limit 00001111 00000011 mod From Register/Memory r/m reg 14, 16 (Note 59) 1 9, 11, 16 ARPL = Adjust Requested Privilege Level: From Register/Memory 01100011 mod r/m reg 10, 11 2 (Note 59) 8, 9 VERR = Verify Read 00001111 00000000 mod Access: Register/Memory r/m 100 14, 16 1 (Note 59) 9, 11, 16 VERR = Access: 101 1 14, 16 (Note 59) 9, 11, 16 Verify Write 00001111 00000000 mod r/m Shaded areas indicate instructions not available in 80G86/88 microsystems. FN2947 Rev.3.00 January 28, 2008 Page 63 of 65 80C286 FN2947 Rev.3.00 January 28, 2008 80C286 Machine Instruction Encoding Matrix LO HI 0 1 2 3 4 5 6 7 8 9 A B C D E F ADD b, f, r/m ADD w, f, r/m ADD b, t, r/m ADD w, t, r/m ADD b, ia ADD w, ia PUSH ES POP ES OR b, f, r/m OR w, f, r/m OR b, t, r/m OR w, t, r/m OR b, i OR w, i PUSH CS PVAM n 0 1 ADC b, f, r/m ADC w, f, r/m ADC b, t, r/m ADC w, t, r/m ADC b, ia ADC w, ia PUSH SS POP SS SBB b, f, r/m SBB w, f, r/m SBB b, t, r/m SBB w, t, r/m SBB b, i SBB w, i PUSH DS POP DS AND b, f, r/m AND w, f, r/m AND b, t, r/m AND w, t, r/m AND b, ia AND w, ia SEG =ES DAA SUB b, f, r/m SUB w, f, r/m SUB b, t, r/m SUB w, t, r/m SUB b, i SUB w, i SEG =CS DAS 2 XOR b, f, r/m XOR w, f, r/m XOR b, t, r/m XOR w, t, r/m XOR b, ia XOR w, ia SEG =SS AAA CMP b, f, r/m CMP w, f, r/m CMP b, t, r/m CMP w, t, r/m CMP b, i CMP w, i SEG =DS AAS 3 4 INC AX INC CX INC DX INC BX INC SP INC BP INC SI INC DI DEC AX DEC CX DEC DX DEC BX DEC SP DEC BP DEC SI DEC DI 5 PUSH AX PUSH CX PUSH DX PUSH BX PUSH SP PUSH SI PUSH SI PUSH DI POP AX POP CX POP DX POP BX POP SP POP BP POP SI POP DI PUSHA POPA BOUND ARPL PUSH w, i IMUL w, t, r/m, i PUSH b, i IMUL b, t, r/m, i INSB INSW OUTSB OUTSW JO JNO JB/ JNAE JNB/ JAE JE/ JZ JNE/ JNZ JBE/ JNA JNBE/ JA JS JNS JP/ JPE JNP/ JPO JL/ JNGE JNL/ JGE JLE/ JNG JNLE/ JG Immed b, r/m Immed w, r/m Immed b, r/m Immed is, r/m TEST b, r/m TEST w, r/m XCHG b, r/m XCHG w, r/m MOV b, f, r/m MOV w, f, r/m MOV b, t, r/m MOV w, t, r/m MOV sr, f, r/m LEA 8 MOV sr, t, r/m POP r/m XCHG AX XCHG CX XCHG DX XCHG BX XCHG SP XCHG BP XCHG SI XCHG DI CBW CWD CALL i, d WAIT PUSHF POPF SAHF LAHF 9 MOV m-AL MOV m-AX MOV AL-m MOV AX-m MOVSB MOVSW CMPSB CMPSW TEST b, i, a TEST w, i, a STOSB STOSW LODSB LODSW SCASB SCASW A B MOV i-AL MOV i-CL MOV i-DL MOV i-BL MOV i-AH MOV i-CH MOV i-DH MOV i-BH MOV i-AX MOV i-CX MOV i-DX MOV i-BX MOV i-SP MOV i-BP MOV i-SI MOV i-DI Shift b, i Shift w, i RET (i+SP) RET LES LDS MOV b, i, r/m MOV w, i, r/m ENTER LEAVE RET I, (i+SP) RET I INT Type 3 INT (any) INTO IRET C Shift b Shift w Shift b, CL AAM AAD XLAT D ESC 0 ESC 1 ESC 2 ESC 3 ESC 4 ESC 5 ESC 6 ESC 6 ESC 7 LOOP JCXZ IN b IN w OUT b OUT w CALL d JMP d JMP i, d JMP si, d IN DX, b IN DX, w OUT DX, b OUT DX, w REP REPZ HLT CMC Grp 1 b, r/m Grp 1 w, r/m CLC STC CLI STI CLD STD Grp 2 b, r/m Grp 2 w, r/m 6 7 Page 64 of 65 E LOOPNZ/ LOOPZ/ LOOPNE LOOPE LOCK F 80C286 where: 80C286 Machine Instruction Encoding Matrix mod r/mm (Continued) 000 001 010 011 100 101 110 111 Immed ADD OR ADC SBB AND SUB XOR CMP Shift ROL ROR RCL RCR SHL/SAL SHR - SAR Grp 1 TEST - NOT NEG MUL IMUL DIV IDIV Grp 2 INC DEC CALL id CALL l, id JMP id JMP l, id PUSH - PVAM 0 SLDT STR LLDT LTR VERR VERW - - PVAM 1 SGDT SIDT LGDT LIDT SMSW - LMSW - PVAM 2 LAR PVAM 3 LSL PVAM 6 CLTS b d f i ia id is l n = = = = = = = = = byte operation direct from CPU reg immediate immediate to AX indirect immediate byte sign extension long i.e., intersegment 2nd byte of PVAM instruction m r/m is sr t v w z = = = = = = = = memory EA is second byte short intrasegment segment register to CPU register variable word operation zero Footnotes The Effective Address (EA) of the memory operand is computed according to the mod and r/m fields: reg is assigned according to the following: REG SEGMENT REGISTER if mod = 11 then r/m is treated as a REG field 00 ES if mod = 00 then DISP = 0†, disp-low and disp-high are absent 01 CS if mod = 01 then DISP = disp-low sign extended to 16 bits, disp-high is absent if mod = 10 then DISP = disp-high: disp-low if r/m = 000 then EA = (BX) + (SI) + DISP if r/m = 001 then EA = (BX) + (DI) + DISP if r/m = 010 then EA = (BP) + (SI) + DISP if r/m = 011 then EA = (BP) + (DI) + DISP 10 SS 11 DS REG is assigned according to the following table: 16-BIT (w = 1) 8-BIT (w = 0) 000 AX 000 AL 001 CX 001 CL 010 DX 010 DL 011 BX 011 BL if r/m = 100 then EA = (SI) + DISP 100 SP 100 AH if r/m = 101 then EA = (DI) + DISP 101 BP 101 CH if r/m = 110 then EA + (BP) + DISP (Note 60) 110 SI 110 DH 111 DI 111 BH if r/m = 111 then EA = (BX) + DISP DISP follows 2nd byte of instruction (before data is required) NOTE: 59. Except if mod = 00 and r/m = 110 then EQ = disp-high: disp-low. Segment Override Prefix 0 0 1 FN2947 Rev.3.00 January 28, 2008 reg The physical addresses of all operands addressed by the BP register are computed using the SS segment register. The physical addresses of the destination operands of the string primitive operations (those addressed by the DI register) are computed using the ES segment, which may not be overridden. 1 1 0 Page 65 of 65