VRS51X550

VRS51x550/560 Datasheet Rev 1.3 Versa 8051 MCUs with 8/16KB Flash Overview The VRS51x550 and VRS51x560 are low-cost 8-bit microcontrollers based on the standard 80C51 microcontroller architecture. They are pin compatible drop-in replacements for the 8051 Ideal for a wide range of applications requiring low to midrange amounts of program/data memory, coupled with streamlined peripheral support, the VRS51x550/560 devices feature 8KB/16KB, of Flash memory (respectively), 256 bytes of RAM, a UART, three 16-bit timers, a watchdog timer and power saving modes. The VRS51x550 is available in 3.3 (VRS51L550) or 5 volt versions (VRS51C550), while the VRS51x560 is available in a 5 volt version (VRS51C560). All devices come in PLCC-44, QFP-44 and DIP-40 packages and operate in the industrial temperature range. Flash can be programmed using a parallel programmer available from Ramtron or with a third party commercial programmer. FIGURE 1: VRS51X550 / VRS51X560 FUNCTIONAL DIAGRAM P 1.4 P 1.3 Feature Set • • • • • • • • • • • • • • • • • • • 80C51/80C52 pin compatible 12 clock periods per machine cycle 8KB / 16KB on-chip Flash memory 256 Bytes on-chip data RAM 32 I/O lines on four 8-bit ports Full duplex serial port (UART) 3, 16-bit Timers/Counters Watchdog Timer 8-bit Unsigned Division / Multiply BCD arithmetic Direct and Indirect Addressing Two levels of interrupt priority and nested interrupts Power saving modes Code protection function Operates at a clock frequency of up to 40MHz Low EMI (inhibit ALE) Programming voltage: 12V Industrial Temperature range (-40°C to +85°C) 5V and 3V versions available (see ordering information) FIGURE 2: VRS51X550 / VRS51X560 PLCC AND QFP PINOUT DIAGRAMS P 1.2 T 2E X/P1 .1 P 0.0/AD 0 P 0.2/AD 2 P1.5 P 1.6 7 6 P0 .1/AD1 T 2/P1 .0 V DD NC 1 P0.3/A D3 40 39 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 #EA NC ALE #PSEN P2.7/A15 8051 PROCESSOR ADDRESS/ DATA BUS P1.7 RESET RXD/P3.0 NC TXD/P3.1 #INT0/P3.2 VRS51x550/560 PLCC-44 8KB / 16KB FLASH 256 Bytes of RAM PORT 0 8 #INT1/P3.3 T0/P3.4 T1/P3.5 17 18 29 28 P2.6/A14 P2.5/A13 # RD /P 3.7 P2 .0 /A8 P2 .1 /A9 P 2.2/A1 0 X TAL 2 X TAL 1 #WR /P 3.6 UART PORT 2 8 P 0 .4 /A D 4 P 0 .5 /A D 5 P 0 .6 /A D 6 P 0 .7 /A D 7 #PSEN P 2 .7 /A 1 5 P 2 .6 /A 1 4 P 2 .5 /A 1 3 23 22 #EA 2 INTERRUPT INPUTS TIMER 0 TIMER 1 TIMER 2 RESET POWER CONTROL WATCHDOG TIMER PORT 3 8 P0.3/AD3 P0.2/AD2 P0.1/AD1 P0.0/AD0 VDD NC T2/P1.0 T2EX/P1.1 P1.2 P1.3 P1.4 44 34 33 ALE NC P 2.4/A1 2 P 2.3/A1 1 V SS NC PORT 1 8 P2.4/A12 P2.3/A11 P2.2/A10 VRS51x550/560 QFP-44 P2.1/A9 P2.0/A8 NC VSS XTAL1 XTAL2 12 11 #RD/P3.7 #WR/P3.6 1 P 1 .5 P 1 .6 P 1 .7 RESET R X D /P 3 .0 NC T X D /P 3 .1 # INT0/P3.2 # IN T 1 /P 3 .3 Ramtron International Corporation 1850 Ramtron Drive Colorado Springs Colorado, USA, 80921 ? ? ? http://www.ramtron.com MCU customer service: 1-800-943-4625, 1-514-871-2447, ext. 208 1-800-545-FRAM, 1-719-481-7000 T 0 /P 3 .4 T 1 /P 3 .5 page 1 of 40 VRS51x550/560 Pin Descriptions for QFP-44 T ABLE 1: PIN DESCRIPTIONS FOR QFP-44/ QFP - 44 Name I/O Function QFP - 44 Name I/O Function 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 P1.5 P1.6 P1.7 RES RXD P3.0 NC TXD P3.1 #INT0 P3.2 #INT1 P3.3 T0 P3.4 T1 P3.5 # WR P3.6 #RD P3.7 XTAL2 XTAL1 VSS NC P2.0 A8 P2.1 A9 P2.2 A10 P2.3 A11 P2.4 A12 P2.5 A13 I/O I/O I/O I I I/O O I/O I I/O I I/O I I/O I I/O O I/O O I/O O I I/O O I/O O I/O O I/O O I/O O I/O O Bit 5 of Port 1 Bit 6 of Port 1 Bit 7 of Port 1 Reset Receive Data Bit 0 of Port 3 No Connect Transmit Data & Bit 1 of Port 3 External Interrupt 0 Bit 2 of Port 3 External Interrupt 1 Bit 3 of Port 3 Timer 0 Bit 4 of Port 3 Timer 1 & 3 Bit 5 of Port Ext. Memory Write Bit 6 of Port 3 Ext. Memory Read Bit 7 of Port 3 Oscillator/Crystal Output Oscillator/Crystal In Ground No Connect Bit 0 of Port 2 Bit 8 of External Memory Address Bit 1 of Port 2 Bit 9 of External Memory Address Bit 2 of Port 2 Bit 10 of External Memory Address Bit 3 of Port 2 & Bit 11 of External Memory Address Bit 4 of Port 2 Bit 12 of External Memory Address Bit 5 of Port 2 Bit 13 of External Memory Address 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 P2.6 A14 P2.7 A15 #PSEN ALE NC #EA P0.7 AD7 P0.6 AD6 P0.5 AD5 P0.4 AD4 P0.3 AD3 P0.2 AD2 P0. 1 AD1 P0.0 AD0 VDD NC T2 P1.0 T2EX P1.1 P1.2 P1.3 P1.4 I/O O I/O O O O I I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I I/O I I/O I/O I/O I/O Bit 6 of Port 2 Bit 14 of External Memory Address Bit 7 of Port 2 Bit 15 of External Memory Address Program Store Enable Address Latch Enable No Connect External Access Bit 7 Of Port 0 Data/Address Bit 7 of External Memory Bit 6 of Port 0 Data/Address Bit 6 of External Memory Bit 5 of Port 0 Data/Address Bit 5 of External Memory Bit 4 of Port 0 Data/Address Bit 4 of External Memory Bit 3 Of Port 0 Data/Address Bit 3 of External Memory Bit 2 of Port 0 Data/Address Bit 2 of External Memory Bit 1 of Port 0 & Data Address Bit 1 of External Memory Bit 0 Of Port 0 & Data Address Bit 0 of External Memory VCC No Connect Timer 2 Clock Out Bit 0 of Port 1 Timer 2 Control Bit 1 of Port 1 Bit 2 of Port 1 Bit 3 of Port 1 Bit 4 of Port 1 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 #EA P2.7/A15 P2.6/A14 33 32 31 30 29 28 27 26 25 24 23 P0.3/AD3 P0.2/AD2 P0.1/AD1 P0.0/AD0 VDD NC T2/P1.0 T2EX/P1.1 P1.2 P1.3 P1.4 34 35 36 37 38 39 40 41 42 43 44 1 2 3 4 5 6 7 8 P2.5/A13 #PS EN NC ALE 22 21 20 P2.4/A12 P2.3/A11 P2.2/A10 P2.1/A9 P2.0/A8 NC VSS XTAL1 XTAL2 #RD/P3.7 #WR/P3.6 VRS51x550/560 QFP-44 19 18 17 16 15 14 13 12 9 10 11 P1.5 P1.6 P1.7 T XD/P3.1 #INT0/P3.2 #INT1/P3.3 ________________________________________________________________________________________________ www.ramtron.com page 2 of 40 RX D/P3.0 T0/P3.4 T1/P3.5 RE SET NC VRS51x550/560 Pin Descriptions for PLCC-44 T ABLE 2: PIN DESCRIPTIONS FOR PLCC-44 PLCC - 44 Name I/O Function PLCC - 44 Name I/O Function 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 NC T2 P1.0 T2EX P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RES RXD P3.0 NC TXD P3.1 #INT0 P3.2 #INT1 P3.3 T0 P3.4 T1 P3.5 # WR P3.6 #RD P3.7 XTAL2 XTAL1 VSS NC I I/O I I/O I/O I/O I/O I/O I/O I/O I I I/O O I/O I I/O I I/O I I/O I I/O O I/O O I/O O I - No Connect Timer 2 Clock Out Bit 0 of Port 1 Timer 2 Control Bit 1 of Port 1 Bit 2 of Port 1 Bit 3 of Port 1 Bit 4 of Port 1 Bit 5 of Port 1 Bit 6 of Port 1 Bit 7 of Port 1 Reset Receive Data Bit 0 of Port 3 No Connect Transmit Data & Bit 1 of Port 3 External Interrupt 0 Bit 2 of Port 3 External Interrupt 1 Bit 3 of Port 3 Timer 0 Bit 4 of Port 3 Timer 1 & 3 Bit 5 of Port Ext. Memory Write Bit 6 of Port 3 Ext. Memory Read Bit 7 of Port 3 Oscillator/Crystal Output Oscillator/Crystal In Ground No Connect 24 25 26 27 28 29 30 31 32 33 34 35 36 P2.0 A8 P2.1 A9 P2.2 A10 P2.3 A11 P2.4 A12 P2.5 A13 P2.6 A14 P2.7 A15 #PSEN ALE NC #EA P0.7 AD7 P0.6 I/O O I/O O I/O O I/O O I/O O I/O O I/O O I/O O O O I I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O - 37 AD6 P0.5 38 AD5 P0.4 39 AD4 P0.3 40 AD3 P0.2 41 P 1.2 T 2EX/P1 .1 AD2 P0. 1 AD1 P0.0 AD0 VDD P1 .4 P 1.3 VDD 42 43 P1.5 P 1.6 P1.7 RESET RXD/P3.0 NC TXD/P3.1 #INT0/P3.2 #INT1/P3.3 T0/P3.4 T1/P3.5 7 8 9 10 11 12 13 14 15 16 6 5 4 3 2 44 43 42 41 40 1 39 38 37 36 35 34 33 32 31 30 P0.4/AD4 P0.5/AD5 P0.6/AD6 P0.7/AD7 #EA NC ALE #PSEN P2.7/A15 P2.6/A14 P2.5/A13 44 Bit 0 of Port 2 Bit 8 of External Memory Address Bit 1 of Port 2 Bit 9 of External Memory Address Bit 2 of Port 2 Bit 10 of External Memory Address Bit 3 of Port 2 & Bit 11 of External Memory Address Bit 4 of Port 2 Bit 12 of External Memory Address Bit 5 of Port 2 Bit 13 of External Memory Address Bit 6 of Port 2 Bit 14 of External Memory Address Bit 7 of Port 2 Bit 15 of External Memory Address Program Store Enable Address Latch Enable No Connect External Access Bit 7 Of Port 0 Data/Address Bit 7 of External Memory Bit 6 of Port 0 Data/Address Bit 6 of External Memory Bit 5 of Port 0 Data/Address Bit 5 of External Memory Bit 4 of Port 0 Data/Address Bit 4 of External Memory Bit 3 Of Port 0 Data/Address Bit 3 of External Memory Bit 2 of Port 0 Data/Address Bit 2 of External Memory Bit 1 of Port 0 & Data Address Bit 1 of External Memory Bit 0 Of Port 0 & Data Address Bit 0 of External Memory VCC P0 .0 /A D0 P0 .1/AD 1 P0 .2/AD2 VRS51x550/560 PLCC-44 17 18 19 20 P 0.3/AD3 29 T 2/P1.0 21 22 23 24 25 26 27 28 # RD/P3.7 NC P 2.0/A8 P 2.1/A9 P2 .2 /A 10 P2 .3 /A1 1 XTAL 2 XTAL 1 #WR/P3.6 ________________________________________________________________________________________________ www.ramtron.com page 3 of 40 P2 .4 /A1 2 VSS NC VRS51x550/560 Pin Descriptions for DIP-40 T ABLE 3: PIN DESCRIPTIONS FOR DIP-40 DIP40 Name I/O Function DIP40 Name I/O Function 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 T2 P1.0 T2EX P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RESET RXD P3.0 TXD P3.1 #INT0 P3.2 #INT1 P3.3 T0 P3.4 T1 P3.5 # WR P3.6 #RD P3.7 XTAL2 XTAL1 VSS I I/O I I/O I/O I/O I/O I/O I/O I/O I I I/O O I/O I I/O I I/O I I/O I I/O O I/O O I/O O I - Timer 2 Clock Out Bit 0 of Port 1 Timer 2 Control Bit 1 of Port 1 Bit 2 of Port 1 Bit 3 of Port 1 Bit 4 of Port 1 Bit 5 of Port 1 Bit 6 of Port 1 Bit 7 of Port 1 Reset Receive Data Bit 0 of Port 3 Transmit Data & Bit 1 of Port 3 External Interrupt 0 Bit 2 of Port 3 External Interrupt 1 Bit 3 of Port 3 Timer 0 Bit 4 of Port 3 Timer 1 & 3 Bit 5 of Port Ext. Memory Write Bit 6 of Port 3 Ext. Memory Read Bit 7 of Port 3 Oscillator/Crystal Output Oscillator/Crystal In Ground 21 22 23 24 25 26 27 28 29 30 31 32 P2.0 A8 P2.1 A9 P2.2 A10 P2.3 A11 P2.4 A12 P2.5 A13 P2.6 A14 P2.7 A15 #PSEN ALE #EA / VPP P0.7 AD7 P0.6 I/O O I/O O I/O O I/O O I/O O I/O O I/O O I/O O O O I I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O I/O - 33 AD6 P0.5 34 AD5 P0.4 35 AD4 P0.3 36 T2 / P1.0 T2EX / P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 RESET RXD / P3.0 TXD / P3.1 #INT0 / P3.2 #INT1 / P3.3 T0 / P3.4 T1 / P3.5 #WR / P3.6 #RD / P3.7 XTAL2 XTAL1 VSS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 VDD P0.0 / AD0 P0.1 / AD1 P0.2 / AD2 P0.3 / AD3 P0.4 / AD4 P0.5 / AD5 P0.6 / AD6 P0.7 / AD7 #EA / VPP ALE PSEN P2.7 / A15 P2.6 / A14 P2.5 / A13 P2.4 / A12 P2.3 / A11 P2.2 / A10 P2.1 / A9 P2.0 / A8 AD3 P0.2 37 38 39 40 AD2 P0. 1 AD1 P0.0 AD0 VDD Bit 0 of Port 2 Bit 8 of External Memory Address Bit 1 of Port 2 Bit 9 of External Memory Address Bit 2 of Port 2 Bit 10 of External Memory Address Bit 3 of Port 2 & Bit 11 of External Memory Address Bit 4 of Port 2 Bit 12 of External Memory Address Bit 5 of Port 2 Bit 13 of External Memory Address Bit 6 of Port 2 Bit 14 of External Memory Address Bit 7 of Port 2 Bit 15 of External Memory Address Program Store Enable Address Latch Enable External Access Flash programming voltage input Bit 7 Of Port 0 Data/Address Bit 7 of External Memory Bit 6 of Port 0 Data/Address Bit 6 of External Memory Bit 5 of Port 0 Data/Address Bit 5 of External Memory Bit 4 of Port 0 Data/Address Bit 4 of External Memory Bit 3 Of Port 0 Data/Address Bit 3 of External Memory Bit 2 of Port 0 Data/Address Bit 2 of External Memory Bit 1 of Port 0 & Data Address Bit 1 of External Memory Bit 0 Of Port 0 & Data Address Bit 0 of External Memory Supply input VRS51x550 VRS51x560 DIP-40 32 31 30 29 28 27 26 25 24 23 22 21 ________________________________________________________________________________________________ www.ramtron.com page 4 of 40 VRS51x550/560 Instruction Set Mnemonic Description Size (bytes) 1 2 1 2 1 2 2 2 2 2 2 2 1 2 1 2 1 2 2 2 2 3 2 3 1 2 2 3 1 1 1 1 1 1 2 2 1 2 1 1 2 3 1 1 2 3 2 2 2 3 3 3 1 2 2 3 3 3 3 2 3 1 Instr. Cycles The following tables describe the instruction set of the VRS51x550/560. The instructions are function and binary code compatible with industry standard 8051s. T ABLE 4: LEGEND FOR INSTRUCTION SET T ABLE Symbol A Rn Direct @Ri rel bit #data #data 16 addr 16 addr 11 Function Accumulator Register R0-R7 Internal register address Internal register pointed to by R0 or R1 (except MOVX) Two's complement offset byte Direct bit address 8-bit constant 16-bit constant 16-bit destination address 11-bit destination address T ABLE 5: VRS51X550/VRS51X560 INSTRUCTION SET Mnemonic Description Size (bytes) 1 2 1 2 1 2 1 2 1 2 1 2 1 1 2 1 1 1 2 1 1 1 1 1 1 2 1 2 2 3 1 2 1 2 2 3 1 2 1 2 2 3 1 1 1 1 1 1 1 Instr. Cycles Arithmetic instructions ADD A, Rn Add register to A ADD A, direct Add direct byte to A ADD A, @Ri Add data memory to A ADD A, #data Add immediate to A ADDC A, Rn Add register to A with carry ADDC A, direct Add direct byte to A with carry ADDC A, @Ri Add data memory to A with carry ADDC A, #data Add immediate to A with carry SUBB A, Rn Subtract register from A with borrow SUBB A, direct Subtract direct byte from A with borrow SUBB A, @Ri Subtract data mem from A with borrow SUBB A, #data Subtract immediate from A with borrow INC A Increment A INC Rn Increment register INC direct Increment direct byte INC @Ri Increment data memory DEC A Decrement A DEC Rn Decrement register DEC direct Decrement direct byte DEC @Ri Decrement data memory INC DPTR Increment data pointer MUL AB Multiply A by B DIV AB Divide A by B DA A Decimal adjust A Logical Instructions ANL A, Rn AND register to A ANL A, direct AND direct byte to A ANL A, @Ri AND data memory to A ANL A, #data AND immediate to A ANL direct, A AND A to direct byte ANL direct, #data AND immediate data to direct byte ORL A, Rn OR register to A ORL A, direct OR direct byte to A ORL A, @Ri OR data memory to A ORL A, #data OR immediate to A ORL direct, A OR A to direct byte ORL direct, #data OR immediate data to direct byte XRL A, Rn Exclusive-OR register to A XRL A, direct Exclusive-OR direct byte to A XRL A, @Ri Exclusive-OR data memory to A XRL A, #data Exclusive-OR immediate to A XRL direct, A Exclusive-OR A to direct byte XRL direct, #data Exclusive-OR immediate to direct byte CLR A Clear A CPL A Compliment A SWAP A Swap nibbles of A RL A Rotate A left RLC A Rotate A left through carry RR A Rotate A right RRC A Rotate A right through carry 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 4 4 1 1 1 1 1 1 2 1 1 1 1 1 2 1 1 1 1 1 2 1 1 1 1 1 1 1 Boolean Instruction CLR C Clear Carry bit CLR bit Clear bit SETB C Set Carry bit to 1 SETB bit Set bit to 1 CPL C Complement Carry bit CPL bit Complement bit ANL C,bit Logical AND between Carry and bit ANL C,#bit Logical AND between Carry and not bit ORL C,bit Logical ORL between Carry and bit ORL C,#bit Logical ORL between Carry and not bit MOV C,bit Copy bit value into Carry MOV bit,C Copy Carry value into Bit Data Transfer Instructions MOV A, Rn Move register to A MOV A, direct Move direct byte to A MOV A, @Ri Move data memory to A MOV A, #data Move immediate to A MOV Rn, A Move A to register MOV Rn, direct Move direct byte to register MOV Rn, #data Move immediate to register MOV direct, A Move A to direct byte MOV direct, Rn Move register to direct byte MOV direct, direct Move direct byte to direct byte MOV direct, @Ri Move data memory to direct byte MOV direct, #data Move immediate to direct byte MOV @Ri, A Move A to data memory MOV @Ri, direct Move direct byte to data memory MOV @Ri, #data Move immediate to data memory MOV DPTR, #data Move immediate to data pointer MOVC A, @A+DPTR 1 1 1 1 1 1 2 2 2 2 1 2 1 1 1 1 1 2 1 1 2 2 2 2 1 2 1 2 2 2 2 2 2 2 2 2 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 Move code byte relative DPTR to A MOVC A, @A+PC Move code byte relative PC to A MOVX A, @Ri Move external data (A8) to A MOVX A, @DPTR Move external data (A16) to A MOVX @Ri, A Move A to external data (A8) MOVX @DPTR, A Move A to external data (A16) PUSH direct Push direct byte onto stack POP direct Pop direct byte from stack XCH A, Rn Exchange A and register XCH A, direct Exchange A and direct byte XCH A, @Ri Exchange A and data memory XCHD A, @Ri Exchange A and data memory nibble Branching Instructions ACALL addr 11 Absolute call to subroutine LCALL addr 16 Long call to subroutine RET Return from subroutine RETI Return from interrupt AJMP addr 11 Absolute jump unconditional LJMP addr 16 Long jump unconditional SJMP rel Short jump (relative address) JC rel Jump on carry = 1 JNC rel Jump on carry = 0 JB bit, rel Jump on direct bit = 1 JNB bit, rel Jump on direct bit = 0 JBC bit, rel Jump on direct bit = 1 and clear JMP @A+DPTR Jump indirect relative DPTR JZ rel Jump on accumulator = 0 JNZ rel Jump on accumulator 1= 0 CJNE A, direct, rel Compare A, direct JNE relative CJNE A, #d, rel Compare A, immediate JNE relative CJNE Rn, #d, rel Compare reg, immediate JNE relative CJNE @Ri, #d, rel Compare ind, immediate JNE relative DJNZ Rn, rel Decrement register, JNZ relative DJNZ direct, rel Decrement direct byte, JNZ relative Miscellaneous Instruction NOP No operation Rn: Any of the register R0 to R7 @Ri: Indirect addressing using Register R0 or R1 #data: immediate Data provided with Instruction #data16: Immediate data included with instruction bit: address at the bit level rel: relative address to Program counter from +127 to –128 Addr11: 11-bit address range Addr16: 16-bit address range #d: Immediate Data supplied with instruction ________________________________________________________________________________________________ www.ramtron.com page 5 of 40 VRS51x550/560 Special Function Registers (SFR) Addresses 80h to FFh of the SFR address space can be accessed in direct addressing mode only. The following table lists the VRS51x550/560 special function registers. T ABLE 6: SPECIAL FUNCTION REGISTERS (SFR) SFR Register P0 SP DPL DPH Reserved PCON TCON TMOD TL0 TL1 TH0 TH1 P1 SCON SBUF WDTCON P2 IE P3 IP SYSCON T2CON RCAP2L RCAP2H TL2 TH2 PSW ACC B SFR Adrs 80h 81h 82h 83h 84h 87h 88h 89h 8Ah 8Bh 8Ch 8Dh 90h 98h 99h 9Fh A0h A8h B0h B8h BFh C8h CAh CBh CCh CDh D0h E0h F0h Bit 7 SMOD TF1 GATE1 SM0 WDTE EA WDRESET TF2 CY - Bit 6 TR1 C/T1 SM1 EXF2 AC - Bit 5 TF0 M1.1 SM2 WDCLR ET2 PT2 RCLK F0 - Bit 4 TR0 M0.1 REN ES PS TCLK RS1 - Bit 3 GF1 IE1 GATE0 TB8 ET1 PT1 EXEN2 RS0 - Bit 2 GF0 IT1 C/T0 RB8 WDPS2 EX1 PX1 TR2 OV - Bit 1 PDOWN IE0 M1.0 TI WDPS1 ET0 PT0 C/T2 - Bit 0 IDLE IT0 M0.0 RI WDPS0 EX0 PX0 ALEI CP/RL2 P - Reset Value 00000000b 00000000b 00000000b 00000000b 0*0**000b 00000000b 00000000b 0******0b 00000000b 00000000b 00000000b ______________________________________________________________________________________________ www.ramtron.com page 6 of 40 VRS51x550/560 Program Memory Program Memory The VRS51x550 includes 8KB of on-chip Program Flash memory. The VRS51x560 includes 16KB Program Flash memory. FIGURE 3: VRS51X560 / VRS51X550 INTERNAL PROGRAM MEMORY 3FFFh Data Pointer The VRS51x550 and VRS51x560 each have one 16-bit data pointer. The DPTR is accessed through two SFR addresses: DPL located at address 82h and DPH located at address 83h. Data Memory The VRS51x550 and VRS51x560 each have a total of: 256 bytes of RAM configured like the internal memory structure of a standard 8052. FIGURE 4: VRS51X550 /VRS51X560 RAM MEMORY OVERVIEW VRS51x560 Flash Memory (16K Bytes) 1FFFh RM51x550 Flash Memory (8K Bytes) 0000h 0000h Program Status Word Register The PSW register is a bit addressable register that contains the status flags (CY, AC, OV, P), user flag (F0) and register bank select bits (RS1, RS0) of the 8051 processor. T ABLE 7: PROGRAM STATUS WORD REGISTER (PSW) - SFR DOH Lower 128 bytes (00h to 7Fh, Bank 0 & Bank 1) The lower 128 bytes of data memory (from 00h to 7Fh) is summarized as follows: • • 1 0 P 7 CY Bit 7 6 5 4 3 2 1 0 6 AC 5 F0 4 RS1 3 RS0 2 OV • • Address range 00h to 7Fh can be accessed in direct and indirect addressing modes. Address range 00h to 1Fh includes R0-R7 registers area. Address range 20h to 2Fh is bit addressable. Address range 30h to 7Fh is not bit addressable and can be used as general-purpose storage. Mnemonic CY AC F0 RS1 RS0 OV P Description Carry Bit Auxiliary Carry Bit from bit 3 to 4. User definer flag R0-R7 Registers bank select bit 0 R0-R7 Registers bank select bit 1 Overflow flag Parity flag Upper 128 bytes (80h to FFh, Bank 2 & Bank 3) The upper 128 bytes of data memory (from 80h to FFh) can be accessed using indirect addressing or by using the bank mapping in direct addressing mode. FIGURE 5: VRS51X550 / VRS51X560 RAM STRUCTURE FFh FFh RS1 0 0 1 1 RS0 0 1 0 1 Active Bank 0 1 2 3 Address 00h-07h 08h-0Fh 10h-17h 18-1Fh 128 Bytes of Indirect Access RAM (SP, R0,R1) SFR Area Direct or Bit Access Only DPH DPL SP 85 84 83 82 81 80 P0 80h 7Fh 80 Bytes of General Purpose RAM 30h 2Fh 7F 77 7E 76 7D 75 7C 74 7B 73 7A 72 79 71 78 70 0F 0E 06 0D 05 0C 04 0B 03 0A 02 09 01 08 00 20h 07 18h 10h 08h 00h R7 R0 R7 R0 R7 R0 R7 R0 Registers Bank 3 Registers Bank 2 Registers Bank 1 Registers Bank 0 ______________________________________________________________________________________________ www.ramtron.com page 7 of 40 VRS51x550/560 Description of Peripherals System Control Register The SYSCON register is used for system control and is described in the following table. The WDRESET bit (7) indicates whether the system has been reset due to overflow of the watchdog timer. Bit 0 of the SYSCON register is the ALE output inhibit bit. Setting this bit to 1 will inhibit the Fosc/6 clock signal output to the ALE pin. T ABLE 8: SYSTEM CONTROL REGISTER (SYSCON) – SFR BFH These power saving modes are controlled by the PDOWN and IDLE bits of the PCON register at address 87h. T ABLE 9: POWER CONTROL REGISTER (PCON) - SFR 87H 7 6 5 4 Unused 3 2 1 RAM1 0 RAM0 Bit 7 Mnemonic SMOD Description 1: Double the baud rate of the serial port frequency that was generated by Timer 1. 0: Normal serial port baud rate generated by Timer 1. 7 WDRESET 6 5 4 3 Unused 2 1 XRAME 0 ALEI Bit 7 Mnemonic WDRESET 6 5 4 3 2 1 0 Unused Unused Unused Unused Unused Unused ALEI Description This is the watchdog timer reset bit. It will be set to 1 when the reset signal generated by WDT overflows. ALE output inhibit bit, which is used to reduce EMI. 6 5 4 3 2 1 0 GF1 GF0 P DOWN IDLE General Purpose Flag General Purpose Flag Power Down mode control bit Idle mode control bit Power Control Register VRS51x550/560 devices provide two power saving modes: Idle and Power Down. These two modes serve to reduce the power consumption of the device. In Idle mode, the processor is stopped but the oscillator continues to run. The contents of the RAM, I/O state and SFR registers are maintained and the timer and external interrupts are left operational. The processor will be woken up when an external event, triggering an interrupt, occurs. In Power Down mode, the VRS51x550/560 oscillator and peripherals are disabled. The contents of the RAM and the SFR registers, however, are maintained. The minimum VCC in Power Down mode is 2V. ______________________________________________________________________________________________ www.ramtron.com page 8 of 40 VRS51x550/560 Input/Output Ports The VRS51x550 and VRS51x560 each have a total of 32 bi-directional I/O lines grouped into four 8-bit I/O ports. These I/Os can be individually configured as inputs or outputs. With the exception of the P0 I/Os, which are of the open drain type, each I/O consists of a transistor connected to ground and a weak pull-up resistor. Writing a 0 in a given I/O port bit register will activate the transistor connected to Vss. This will bring the I/O to a LOW level. Read Pin FIGURE 6: INTERNAL STRUCTURE OF ONE OF THE E IGHT I/O PORT LINES Read Register Internal Bus Q D Flip-Flop Output Stage IC Pin Write to Register Q Writing a 1 into a given I/O port bit register deactivates the transistor between the pin and ground. In this case, the pull-up resistor will bring the corresponding pin to a HIGH level. To use a given I/O as an input, a 1 must be written into its associated port register bit. By default, upon reset all the I/Os are configured as inputs. Structure of the P1, P2, P3 The following figure describes the general structure of the P1, P2 and P3 ports. Note that the figure below does not show the intermediary logic that connects the register output with the output stage because this logic varies with the auxiliary function of each port. FIGURE 7: GENERAL STRUCTURE OF THE O UTPUT STAGE OF P1, P2 AND P3 General Structure of an I/O Port The following elements establish the link between the core unit and the pins of the microcontroller: • • Special Function Register (same name as port) Output Stage Amplifier (the structure of this element varies with its auxiliary function) Read Register Vcc Pull-up Network From the next figure, one can see that the D flip-flop stores the value received from the internal bus after receiving a write signal from the core. Also, note that the Q output of the flip-flop can be linked to the internal bus by executing a read instruction. This is how one would read the content of the register. It is also possible to link the value of the pin to the internal bus. This is done by the “read pin” instruction. In short, the user may read the value of the register or the pin. Internal Bus Q IC Pin D Flip-Flop Write to Register Q X1 Read Pin Each line may be used independently as a logical input or output. When used as an input, the corresponding port register bit must be high. ______________________________________________________________________________________________ www.ramtron.com page 9 of 40 VRS51x550/560 Structure of Port 0 The internal structure of P0 is shown below. The auxiliary function of this port requires a particular logic. As opposed to the other ports, P0 is truly bi-directional. In other words, when used as an input, it is considered to be in a floating logical state (high impedance state). This arises from the absence of the internal pull-up resistance. The pull-up resistance is actually replaced by a transistor that is only used when the port is configured to access the external memory/data bus (EA=0). When used as an I/O port, P0 acts as an open drain port and the use of an external pull-up resistor is likely to be required for most applications. FIGURE 8: PORT P0’ S PARTICULAR STRUCTURE Internal Bus Q IC Pin D Flip-Flop Address A0/A7 Read Register Control Port P0 and P2 as Address and Data Bus The output stage may receive data from two sources: • • The outputs of register P0 or the bus address itself multiplexed with the data bus for P0 The outputs of the P2 register or the high byte (A8 through A15) of the bus address for the P2 port FIGURE 9: P2 PORT STRUCTURE Read Register Vcc Address Pull-up Network Write to Register Q Control X1 Vcc Read Pin Internal Bus Q IC Pin D Flip-Flop X1 Write to Register Q Read Pin When the ports are used as an address or data bus, the special function registers P0 and P2 are disconnected from the output stage. The 8 bits of the P0 register are forced to 1 and the content of the P2 register remains constant. When P0 is used as an external memory bus input (for a MOVX instruction, for example), the outputs of the register are automatically forced to 1. Auxiliary Port 1 Functions The Port 1 I/O pins are shared with the T2EX and T2 inputs as shown below: Pin P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7 Mnemonic T2 T2EX Function Timer 2 counter input Timer 2 Auxiliary input ______________________________________________________________________________________________ www.ramtron.com page 10 of 40 VRS51x550/560 Auxiliary P3 Port Functions The Port 3 I/O pins are shared with the UART interface, the INT0 and INT1 interrupts, the Timer 0 and Timer 1 inputs and the #WR and #RD lines when external memory access is performed. FIGURE 10: P3 PORT STRUCTURE Software Particularities Concerning the Ports Some instructions allow the user to read the logic state of the output pin, while others allow the user to read the content of the associated port register. These instructions are called read-modify-write instructions. A list of these instructions may be found in the table below. Upon execution of these instructions, the content of the port register (at least 1 bit) is modified. The other read instructions take the present state of the input into account. For example, the instruction ANL P3, #01h obtains the value in the P3 register; performs the desired logic operation with the constant 01h; and recopies the result into the P3 register. When users want to take the present state of the inputs into account, they must first read these states and perform an AND operation between the reading and the constant. MOV A, P3; State of the inputs in the accumulator ANL A, #01; AND operation between P3 and 01h When the port is used as an output, the register contains information on the state of the output pins. Measuring the state of an output directly on the pin is inaccurate because the electrical level depends mostly on the type of charge that is applied to it. The functions shown below take the value of the register rather than that of the pin. T ABLE 11: LIST OF INSTRUCTIONS THAT READ AND MODIFY THE PORT USING REGISTER VALUES Read Register Auxiliary Function: Output Vcc IC Pin X1 Internal Bus Q D Flip-Flop Write to Register Q Read Pin Auxiliary Function: Input The following table describes the auxiliary function of the Port 3 I/O pins. T ABLE 10: P3 AUXILIARY F UNCTION T ABLE Pin P3.0 Mnemonic RXD P3.1 TXD P3.2 P3.3 P3.4 P3.5 P3.6 P3.7 INT0 INT1 T0 T1 WR RD Function Serial Port: Receive data in asynchronous mode. Input and output data in synchronous mode. Serial Port: Transmit data in asynchronous mode. Output clock value in synchronous mode. External Interrupt 0 Timer 0 Control Input External Interrupt 1 Timer 1 Control Input Timer 0 Counter Input Timer 1 Counter Input Write signal for external memory Read signal for external memory Instruction ANL ORL XRL JBC CPL INC DEC DJNZ MOV P., C CLR P.x SETB P.x Function Logical AND ex: ANL P0, A Logical OR ex: ORL P2, #01110000B Exclusive OR ex: XRL P1, A Jump if the bit of the port is set to 0 Complement one bit of the port Increment the port register by 1 Decrement the port register by 1 Decrement by 1 and jump if the result is not equal to 0 Copy the held bit C to the port Set the port bit to 0 Set the port bit to 1 ______________________________________________________________________________________________ www.ramtron.com page 11 of 40 VRS51x550/560 Port Operation Timing Writing to a Port (Output) When an operation results in a modification of the content in a port register, the new value is placed at the output of the D flip-flop during the T12 period of the last machine cycle that the instruction needed to execute. It is important to note, however, that the output stage only samples the output of the registers on the P1 phase of each period. It follows that the new value only appears at the output after the T12 period of the following machine cycle. Reading a Port (Input) The reading of an I/O pin takes place: • • • During T9 cycle for P0, P1 During T10 cycle for P2, P3 When the ports are configured as I/Os (see Figure 25) In order to be sampled, the signal duration present on the I/O inputs must be longer than Fosc/12. I/O Ports Driving Capability The maximum allowable continuous current that the device can sink on an I/O port is defined by the following: Maximum sink current on one given I/O Maximum total sink current for P0 Maximum total sink current for P1, 2, 3 Maximum total sink current on all I/O 10mA 26mA 15mA 70mA It is not recommended to exceed the sink current outlined in the above table. Doing so will likely make the low-level output voltage exceed the device’s specification and will likely affect device reliability. The VRS51x550/VRS51x560 designed to source current. I/O ports are not ______________________________________________________________________________________________ www.ramtron.com page 12 of 40 VRS51x550/560 Timers The VRS51x550 and VRS51x560 each include three 16-bit timers: T0, T1 and T2. The timers can operate in two specific modes: • Event counting mode • Timer mode When operating in counting mode, the counter is incremented each time an external event, such as a transition in the logical state of the timer input (T0, T1, T2 input), is detected. When operating in timer mode, the counter is incremented by the microcontroller’s direct clock pulse or by a divided version of this pulse. T ABLE 12: T IMER MODE CONTROL REGISTER (TMOD) – SFR 89H 7 GATE Bit 7 6 C/T Mnemonic GATE1 5 M1 4 M0 3 GATE 2 C/T 1 M1.0 0 M0.0 6 C/T1 5 4 3 M1.1 M0.1 GATE0 Timer 0 and Timer 1 Timers 0 and 1 have four modes of operation. These modes allow the user to change the size of the counting register or to authorize an automatic reload when provided with a specific value. Timer 1 can also be used as a baud rate generator to generate communication frequencies for the serial interface. Timer 0 and Timer 1 are configured by the TMOD and TCON registers. 2 C/T0 1 0 M1.0 M0.0 Description 1: Enables external gate control (pin INT1 for Counter 1). When INT1 is high, and TRx bit is set (see TCON register), a counter is incremented every falling edge on the T1IN input pin. Selects timer or counter operation (Timer 1). 1 = A counter operation is performed 0 = The corresponding register will function as a timer. Selects mode for Timer/Counter 1 Selects mode for Timer/Counter 1 If set, enables external gate control (pin INT0 for Counter 0). When INT0 is high, and TRx bit is set (see TCON register), a counter is incremented every falling edge on the T0IN input pin. Selects timer or counter operation (Timer 0). 1 = A counter operation is performed 0 = The corresponding register will function as a timer. Selects mode for Timer/Counter 0. Selects mode for Timer/Counter 0. The table below summarizes the four modes of operation of timers 0 and 1. The timer-operating mode is selected by the bits M1 and M0 of the TMOD register. T ABLE 13: T IMER/COUNTER MODE DESCRIPTION SUMMARY M1 0 0 1 M0 0 1 0 Mode Mode 0 Mode 1 Mode 2 Function 13-bit Counter 16-bit Counter 8-bit auto-reload Counter/Timer. The reload value is kept in TH0 or TH1, while TL0 or TL1 is incremented every machine cycle. When TLx overflows, the value of THx is copied to TLx. If Timer 1 M1 and M0 bits are set to 1, Timer 1 stops. 1 1 Mode 3 ______________________________________________________________________________________________ www.ramtron.com page 13 of 40 VRS51x550/560 Timer 0/Timer 1 Counter/Timer Functions Timing Function When operating as a timer, the counter is automatically incremented at every system cycle (Fosc/12). A flag is raised in the event of an overflow and the counter acquires a value of zero. These flags (TF0 and TF1) are located in the TCON register. T ABLE 14: T IMER 0 AND 1 CONTROL REGISTER (TCON) –SFR 88H Operating Modes The user may change the operating mode by varying the M1 and M0 bits of the TMOD SFR. Mode 0 A schematic representation of this mode of operation can be found in Figure 11. From the figure, we notice that the timer operates as an 8-bit counter preceded by a divide-by-32 prescaler composed of the 5LSBs of TL1. The register of the counter is configured to be 13 bits long. When an overflow causes the value of the register to roll over to 0, the TFx interrupt signal goes to 1. The count value is validated as soon as TRx goes to 1 and the GATE bit is 0, or when INTx is 1. FIGURE 11: T IMER/COUNTER 1 MODE 0: 13-BIT COUNTER 7 TF1 6 TR1 5 TF0 4 TR0 3 IE1 2 IT1 1 IE0 0 IT0 Bit 7 Mnemonic TF1 Description Timer 1 Overflow Flag. Set by hardware on Timer/Counter overflow. Cleared by hardware on Timer/Counter overflow. Cleared by hardware when processor vectors to interrupt routine. Timer 1 Run Control Bit. Set/cleared by software to turn Timer/Counter on or off. Timer 0 Overflow Flag. Set by hardware on Timer/Counter overflow. Cleared by hardware when processor vectors to interrupt routine. Timer 0 Run Control Bit. Set/cleared by software to turn Timer/Counter on or off. Interrupt Edge Flag. Set by hardware when external interrupt edge is detected. Cleared when interrupt processed. Interrupt 1 Type Control Bit. Set/cleared by software to specify falling edge/low level triggered external interrupts. Interrupt 0 Edge Flag. Set by hardware when external interrupt edge is detected. Cleared when interrupt processed. Interrupt 0 Type control bit. Set/cleared by software to specify falling edge/low level triggered external interrupts. 6 TR1 5 TF0 CLK ÷12 TL1 CLK 1 C/T =1 Control 0 C/T =0 0 4 7 4 3 2 1 0 TR0 IE1 IT1 IE0 IT0 Mode 0 T1PIN Mode 1 TR1 GATE INT1 PIN 0 TH1 7 TF1 INT Mode 1 Mode 1 is almost identical to Mode 0. They differ in that in Mode 1, the counter uses the full 16 bits and has no prescaler. Mode 2 In this mode, the register of the timer is configured as an 8-bit automatically re-loadable counter. In Mode 2, it is the lower byte TLx that is used as the counter. In the event of a counter overflow, the TFx flag is set to 1 and the value contained in THx, which is preset by software, is reloaded into the TLx counter. The value of THx remains unchanged. Counting Function When operating as a counter, the timer’s register is incremented at every falling edge of the T0, T1 and T2 signals located at the input of the timer. In this case, the signal is sampled at the T10 phase of each machine cycle for Timer 0, Timer 1 and at T9 for Timer 2. When the sampler sees a high immediately followed by a low in the next machine cycle, the counter is incremented. Two machine cycles are required to detect and record an event. This reduces the counting frequency by a factor of 24 (24 times less than the oscillator’s frequency). ______________________________________________________________________________________________ www.ramtron.com page 14 of 40 VRS51x550/560 FIGURE 12: T IMER/COUNTER 1 MODE 2: 8-BIT AUTOMATIC RELOAD CLK ÷12 C/T =0 0 TL1 7 0 1 T1 Pin C/T=1 Control Reload 0 TH1 7 TR1 GATE INT0 PIN TF1 INT Mode 3 In Mode 3, Timer 1 is blocked as if its control bit, TR1, was set to 0. In this mode, Timer 0’s registers TL0 and TH0 are configured as two separate 8-bit counters. Additionally, the TL0 counter uses Timer 0’s control bits C/T, GATE, TR0, INT0, TF0 and the TH0 counter is held in Timer Mode (counting machine cycles) and gains control over TR1 and TF1 from Timer 1. At this point, TH0 controls the Timer 1 interrupt. FIGURE 13: T IMER/COUNTER 0 MODE 3 TH0 CLK 0 7 Control TR1 TF1 INTERRUPT C LK ÷12 TL0 0 C/T =0 CLK 0 7 1 T0PIN C/T =1 Control TF0 INTERRUPT TR0 GATE INT0 PIN ______________________________________________________________________________________________ www.ramtron.com page 15 of 40 VRS51x550/560 Timer 2 Timer 2 is a 16-bit Timer/Counter. Similar to timers 0 and 1, Timer 2 can operate as either an event counter or as a timer. The user may switch functions by writing to the C/T2 bit located in the T2CON special function register. Timer 2 has three operating modes: “AutoLoad” “Capture”, and “Baud Rate Generator”. The T2CON SFR configures the modes of operation of Timer 2. The following table describes each bit in the T2CON special function register. T ABLE 15: T IMER 2 CONTROL REGISTER (T2CON) –SFR C8H 0 CP/RL2 Capture/Reload Select. 1: Capture of Timer 2 value into RCAP2H, RCAP2L is performed if EXEN2=1 and a negative transitions occurs on the T2EX pin. The capture mode requires RCLK and TCLK to be 0. 0: Auto-reload reloads will occur either with Timer 2 overflows or negative transitions at T2EX when EXEN2=1. When either RCK =1 or TCLK =1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow. 7 TF2 6 EXF2 5 RCLK 4 TCLK 3 EXEN2 2 TR2 1 C/T2 0 CP/RL2 As shown below, there are different combinations of control bits that may be used for the mode selection of Timer 2. T ABLE 16: T IMER 2 MODE SELECTION BITS Bit Mnemonic 7 TF2 6 EXF2 5 RCLK Description Timer 2 Overflow Flag: Set by an overflow of Timer 2 and must be cleared by software. TF2 will not be set when either RCLK =1 or TCLK =1. Timer 2 external flag change in state occurs when either a capture or reload is caused by a negative transition on T2EX and EXEN2=1. When Timer 2 is enabled, EXF=1 will cause the CPU to Vector to the Timer 2 interrupt routine. Note that EXF2 must be cleared by software. Serial Port Receive Clock Source. 1: Causes Serial Port to use Timer 2 overflow pulses for its receive clock in modes 1 and 3. 0: Causes Timer 1 overflow to be used for the Serial Port receive clock. Serial Port Transmit Clock. 1: Causes Serial Port to use Timer 2 overflow pulses for its transmit clock in modes 1 and 3. 0: Causes Timer 1 overflow to be used for the Serial Port transmit clock. Timer 2 External Mode Enable. 1: Allows a capture or reload to occur as a result of a negative transition on T2EX if Timer 2 is not being used to clock the Serial Port. 0: Causes Timer 2 to ignore events at T2EX. Start/Stop Control for Timer 2. 1: Start Timer 2 0: Stop Timer 2 Timer or Counter Select (Timer 2) 1: External event counter falling edge triggered. 0: Internal Timer (OSC/12) RCLK + TCLK 0 0 1 X CP/RL2 0 1 X X TR2 1 1 1 0 MODE 16-bit AutoReload Mode 16-bit Capture Mode Baud Rate Generator Mode Off The details of each mode are described below. Capture Mode In capture mode the EXEN2 bit value defines whether the external transition on the T2EX pin will be able to trigger the capture of the timer value. When EXEN2 = 0, Timer 2 acts as a 16-bit timer or counter, which, upon overflowing, will set bit TF2 (Timer 2 overflow bit). This overflow can be used to generate an interrupt. FIGURE 14: T IMER 2 IN CAPTURE MODE FOSC ÷12 4 TCLK 3 EXEN2 0 C/T2 1 T2 Pin TIMER 0 COUNTER TL2 7 0 TH2 7 2 1 TR2 0 TR2 RCAP2L 7 0 RCAP2H 7 C/T2 TF2 T2 EX Pin EXF2 EXEN2 Timer 2 Interrupt When EXEN2 = 1, the above still applies. In addition, it is possible to allow a 1 to 0 transition at the T2EX input to cause the current value stored in the Timer 2 registers (TL2 and TH2) to be captured by the RCAP2L ______________________________________________________________________________________________ www.ramtron.com page 16 of 40 VRS51x550/560 and RCAP2H registers. Furthermore, the transition at T2EX causes bit EXF2 in T2CON to be set, and EXF2, like TF2, can generate an interrupt. Note that both EXF2 and TF2 share the same interrupt vector. Baud Rate Generator Mode The baud rate generator mode is activated when RCLK is set to 1 and/or TCLK is set to 1. This mode will be described in the serial port section. FIGURE 16: T IMER 2 IN AUTOMATIC BAUD GENERATOR MODE FOSC ÷2 Auto-Reload Mode In this mode, there are also two options. The user may choose either option by writing to bit EXEN2 in T2CON. If EXEN2 = 0, when Timer 2 rolls over, it not only sets TF2, but also causes the Timer 2 registers to be reloaded with the 16-bit value in the RCAP2L and RCAP2H registers previously initialised. In this mode, Timer 2 can be used as a baud rate generator source for the serial port. If EXEN2=1, then Timer 2 still performs the above operation, but a 1 to 0 transition at the external T2EX input will also trigger an anticipated reload of the Timer 2 with the value stored in RCAP2L, RCAP2H, and set EXF2. FIGURE 15: T IMER 2 IN AUTO-RELOAD MODE 0 C/T2 1 T2 Pin TIMER 0 COUNTER TL2 7 0 TH2 7 0 TR2 RCAP2L 1 0 0 7 0 RCAP2H 7 ÷16 TCLK 1 0 TX Clock RX Clock ÷16 Timer 1 Overflow ÷2 1 RCLK SMOD T2 EX Pin EXF2 Timer 2 Interrupt Request EXEN2 FOSC ÷12 0 C/T2 1 T2 Pin TIMER 0 COUNTER TL2 7 0 TH2 7 0 TR2 RCAP2L 7 0 RCAP2H 7 TF2 T2 EX Pin EXF2 EXEN2 Timer 2 Interrupt ______________________________________________________________________________________________ www.ramtron.com page 17 of 40 VRS51x550/560 Serial Port The serial port included in the VRS51x550 and the VRS51x560 can operate in full duplex; in other words, it can transmit and receive data simultaneously. This occurs at the same speed if one timer is assigned as the clock source for both transmission and reception, and at different speeds if transmission and reception are each controlled by their own timer. The serial port receive is buffered, which means that it can begin reception of a byte even if the processor has not retrieved the last byte from the receive register. However, if the previously received byte has not been read by the time reception of the next byte is complete, the byte present in the receive buffer will be lost. The SBUF register provides access to the transmit and receive registers of the serial port. Reading from the SBUF register will access the receive register, while a write to the SBUF loads the transmit register.. 2 RB8 9 data bit received in modes 2 and 3. In Mode 1, if SM2 = 0, RB8 is the stop bit that was received. In Mode 0, this bit is not used. This bit must be cleared by software. Transmission Interrupt flag. Automatically set to 1 when: th • The 8 bit has been sent in Mode 0. • Automatically set to 1 when the stop bit has been sent in the other modes. This bit must be cleared by software. Reception Interrupt flag Automatically set to 1 when: th • The 8 bit has been received in Mode 0. • Automatically set to 1 when the stop bit has been sent in the other modes (see SM2 exception). This bit must be cleared by software. T ABLE 18: SERIAL PORT MODES OF OPERATION th 1 TI 0 RI S M0 SM1 Mode Description Baud Rate Serial Port Control Register The SCON (serial port control) register contains control and status information, and includes the ninth data bit for transmit and receive (TB8/RB8 if required) mode selection bits and serial port interrupt bits (TI and RI). T ABLE 17: SERIAL PORT CONTROL REGISTER (SCON) – SFR 98H 0 0 1 1 0 1 0 1 0 1 2 3 Shift Register 8-bit UART 9-bit UART 9-bit UART Fosc/12 Variable Fosc/64 or Fosc/32 Variable Modes of Operation The serial port on the VRS51x550/560 can operate in four different modes. In all four modes, a transmission is initiated by an instruction that uses the SBUF SFR as a destination register. In Mode 0, reception is initiated by setting RI to 0 and REN to 1. An incoming start bit initiates reception in the other modes provided that REN is set to 1. The following section describes the four modes. 7 SM0 6 SM1 5 SM2 4 REN 3 TB8 2 RB8 1 TI 0 RI Bit 7 6 Mnemonic SM0 SM1 5 SM2 Description Bit to select mode of operation (see table below) Bit to select mode of operation (see table below) Multiprocessor communication is possible in modes 2 and 3. In modes 2 or 3 if SM2 is set to 1, RI will th not be activated if the received 9 data bit (RB8) is 0. In Mode 1, if SM2 = 1 then RI will not be activated if a valid stop bit was not received. Serial Reception Enable Bit This bit must be set by software and cleared by software. 1: Serial reception enabled 0: Serial reception disabled th 9 data bit transmitted in modes 2 and 3 This bit must be set by software and cleared by software. 4 REN 3 TB8 ______________________________________________________________________________________________ www.ramtron.com page 18 of 40 VRS51x550/560 Mode 0 In this mode, the serial data exits and enters through the RXD pin. TXD is used to output the shift clock. The signal is composed of 8 data bits starting with the LSB. The baud rate in this mode is 1/12 the oscillator frequency. The SEND signal enables the output of the shift register to the alternate output function line of P3.0 and enables SHIFT CLOCK to the alternate output function line of P3.1. SHIFT CLOCK is high during T11, T12 and T1, T2 and T3, T4 of every machine cycle and low during T5, T6, T7, T8, T9 and T10. At T12 of every machine cycle in which SEND is active, the contents of the transmit shift register are shifted to the right by one position. Zeros come in from the left as data bits shift out to the right. The TX control block sends its final shift and deactivates SEND while setting T1 after certain conditions are fulfilled: The MSB of the data byte is at the output position of the shift register; the 1 that was initially loaded into the ninth position is just to the left of the MSB; and all positions to the left of that contain zeros. Once these conditions are met, the deactivation of SEND and the setting of T1 occur at T1 of the tenth machine cycle after the “write to SBUF” pulse. Reception in Mode 0 RXD P3.0 Internal Bus 1 Write to SBUF S D CLK Q SBUF Shift ZERO DETECTOR RXD P3.0 Shift Clock Shift TXD P3.1 Start TX Control Unit Fosc/12 TX Clock TI Send Serial Port Interrupt RX Clock RI REN RI RX Control Unit Start Shift 1 1 1 1 1 1 1 0 Receive RXD P3.0 Input Function Shift Register SBUF READ SBUF When REN and R1 are set to 1 and 0 respectively, reception is initiated. The bits 11111110 are written to the receive shift register at T12 of the next machine cycle by the RX control unit. In the following phase, the RX control unit will activate RECEIVE. SHIFT CLOCK to the alternate output function line of P3.1 is enabled by RECEIVE. At every machine cycle, SHIFT CLOCK makes transitions at T5 and T11. The contents of the receive shift register are shifted one position to the left at T12 of every machine in which RECEIVE is active. The value that comes in from the right is the value that was sampled at the P3.0 pin at T10 of the same machine cycle. 1’s are shifted out to the left as data bits are shifted in from the right. The RX control block is flagged to do one last shift and load SBUF when the 0 that was initially loaded into the rightmost position arrives at the leftmost position in the shift register. Internal Bus FIGURE 17: SERIAL PORT MODE 0 BLOCK DIAGRAM Transmission in Mode 0 Any instruction that uses SBUF as a destination register may initiate a transmission. The “write to SBUF” signal also loads a 1 into the ninth position of the transmit shift register and tells the TX control block to begin a transmission. The internal timing is such that one full machine cycle will elapse between a write to SBUF instruction and the activation of SEND. ______________________________________________________________________________________________ www.ramtron.com page 19 of 40 VRS51x550/560 Mode 1 For an operation in Mode 1, 10 bits are transmitted through TXD or received through RXD. The transactions are composed of: a Start bit (Low), 8 data bits (LSB first) and one Stop bit (high). The reception is completed once the Stop bit sets the RB8 flag in the SCON register. Either Timer 1 or Timer 2 controls the baud rate in this mode. The following diagram shows the serial port structure when configured in Mode 1. FIGURE 18: SERIAL PORT MODE 1 AND 3 BLOCK DIAGRAM Internal Bus 1 Write to SBUF When a transmission begins, it places the start bit at TXD. Data transmission is activated one bit time later. This activation enables the output bit of the transmit shift register to TXD. One bit time after that, the first shift pulse occurs. In this mode, zeros are clocked in from the left as data bits are shifted out to the right. When the most significant bit of the data byte is at the output position of the shift register, the 1 that was initially loaded into the ninth position is to the immediate left of the MSB, and all positions to the left of that contain zeros. This condition flags the TX control unit to shift one more time. Reception in Mode 1 One to zero transitions at RXD initiate reception. It is for this reason that RXD is sampled at a rate of 16 multiplied by the established baud rate. When a transition is detected, 1FFh is written into the input shift register and the divide-by-16 counter is immediately reset. The divide-by-16 counter is reset in order to align its rollovers with the boundaries of the incoming bit times. In total, there are 16 states in the counter. During the 7th, 8th and 9th counter states of each bit time; the bit detector samples the value of RXD. The accepted value is the value that was seen in at least two of the three samples. The purpose of doing this is for noise rejection. If the value accepted during the first bit time is not zero, the receive circuits are reset and the unit goes back to searching for another one to zero transition. All false start bits are rejected by doing this. If the start bit is valid, it is shifted into the input shift register, and the reception of the rest of the frame will proceed. For a receive operation, the data bits come in from the right as 1’s shift out on the left. As soon as the start bit arrives at the leftmost position in the shift register, (9bit register), it tells the RX control block to perform one last shift operation: to set RI and to load SBUF and RB8. The signal to load SBUF and RB8, and to set RI, will be generated if, and only if, the following conditions are met at the time the final shift pulse is generated: • • Either SM2 = 0 or the received stop bit = 1 RI = 0 Timer 1 Overflow S D CLK Timer 2 Overflow Q SBUF TXD ÷2 01 SMOD ZERO DETECTOR 0 1 TCLK ÷16 Start Shift TX Control Unit Data TX Clock TI Send 0 RCLK 1 ÷16 Serial Port Interrupt RX Clock 1-0 Transition Detector Start RI RX Control Unit Load SBUF SHIFT RXD Bit Detector LOAD SBUF 9-Bit Shift Register Shift SBUF READ SBUF Internal Bus Transmission in Mode 1 Transmission is initiated by any instruction that makes use of SBUF as a destination register. The ninth bit position of the transmit shift register is loaded by the “write to SBUF” signal. This event also flags the TX control unit that a transmission has been requested. It is after the next rollover in the divide-by-16 counter when transmission actually begins at T1 of the machine cycle. It follows that the bit times are synchronized to the divide-by-16 counter and not to the “write to SBUF” signal. ______________________________________________________________________________________________ www.ramtron.com page 20 of 40 VRS51x550/560 If both conditions are met, the stop bit goes into RB8, the 8 data bits go into SBUF and RI is activated. If one of these conditions is not met, the received frame is lost. At this time, whether the above conditions are met or not, the unit goes back to searching for a one to zero transition in RXD. Mode 2 In Mode 2, a total of 11 bits are transmitted through TXD or received through RXD. The transactions are composed of: a Start bit (Low), 8 data bits (LSB first), a programmable ninth data bit and one Stop bit (High). For transmission, the ninth data bit comes from the TB8 bit of SCON. For example, the parity bit P in the PSW could be moved into TB8. In the case of receive, the ninth data bit is automatically written into RB8 of the SCON register. In Mode 2, the baud rate is programmable to either 1/32 or 1/64 the oscillator frequency. RCLK Mode 3 In Mode 3, 11 bits are transmitted through TXD or received through RXD. The transactions are composed of: a Start bit (Low), 8 data bits (LSB first), a programmable ninth data bit and one Stop bit (High). Mode 3 is identical to Mode 2 in all respects but one; the baud rate. Either Timer 1 or Timer 2 generates the baud rate in Mode 3. FIGURE 20: SERIAL PORT MODE 3 BLOCK DIAGRAM Internal Bus 1 Write to SBUF Timer 1 Overflow S D CLK Timer 2 Overflow Q SBUF TXD ÷2 01 SMOD ZERO DETECTOR 0 1 TCLK ÷16 Start Shift TX Control Unit Data TX Clock TI Send 0 1 ÷16 Serial Port Interrupt RI RX Control Unit Load SBUF SHIFT FIGURE 19: SERIAL PORT MODE 2 BLOCK DIAGRAM SAMPLE 1-0 Transition Detector RX Clock Start Internal Bus 1 Write to SBUF RXD Bit Detector LOAD SBUF 9-Bit Shift Register Shift Fosc/2 S D CLK Q SBUF TXD SBUF READ SBUF ÷2 01 SMOD ÷16 Stop Start TX Clock ZERO DETECTOR Internal Bus Shift TX Control Unit TI Data Send ÷16 Serial Port Interrupt RX Clock Control RI RX Control Unit Load SBUF SHIFT Sample 1-0 Transition Detector Start RXD Bit Detector LOAD SBUF 9-Bit Shift Register Shift SBUF READ SBUF Internal Bus ______________________________________________________________________________________________ www.ramtron.com page 21 of 40 VRS51x550/560 Mode 2 and 3: Additional Information As mentioned earlier, for an operation in these modes, 11 bits are transmitted through TXD or received through RXD. The signal comprises: a logical low Start bit, 8 data bits (LSB first), a programmable ninth data bit and one logical high Stop bit. On transmission, the TB8 of the SCON register can be assigned the value of 0 or 1. On receive, the ninth data bit goes into RB8 in SCON. The baud rate is programmable to either 1/32 or 1/64 the oscillator frequency in Mode 2. Mode 3 may have a variable baud rate generated from either Timer 1 or Timer 2 depending on the states of TCLK and RCLK. Transmission in Mode 2 and Mode 3 The transmission is initiated by any instruction that makes use of SBUF as the destination register. The ninth bit position of the transmit shift register is loaded by the “write to SBUF” signal. This event also informs the TX control unit that a transmission has been requested. After the next rollover in the divide-by-16 counter, a transmission actually begins at T1 of the machine cycle. The bit times are synchronized to the divide-by-16 counter and not to the “write to SBUF” signal, as in the previous mode. Transmissions begin when the SEND signal is activated, which places the Start bit at TXD. Data is activated one bit time later. This activation enables the output bit of the transmit shift register to TXD. The first shift pulse occurs one bit time after that. The first shift clocks a Stop bit (1) into the ninth bit position of the shift register to TXD. Thereafter, only zeros are clocked in. Thus, as data bits shift out to the right, zeros are clocked in from the left. When TB8 is at the output position of the shift register, the Stop bit is just to the left of TB8, and all positions to the left of that contain zeros. This condition signals to the TX control unit to shift one more time and set TI, while deactivating SEND. This occurs at the eleventh divideby-16 rollover after “write to SBUF”. Reception in Mode 2 and Mode 3 One to zero transitions at RXD initiate reception. It is for this reason that RXD is sampled at a rate of 16 multiplied by the established baud rate. When a transition is detected, the 1FFh is written into the input shift register and the divide-by-16 counter is immediately reset. During the 7th, 8th and 9th counter states of each bit time; the bit detector samples the value of RXD. The accepted value is the value that was seen in at least two of the three samples. If the value accepted during the first bit time is not zero, the receive circuits are reset and the unit goes back to searching for another one to zero transition. If the start bit is valid, it is shifted into the input shift register and the reception of the rest of the frame will proceed. For a receive operation, the data bits come in from the right as 1’s shift out on the left. As soon as the Start bit arrives at the leftmost position in the shift register (9-bit register), it tells the RX control block to do one more shift to set RI and load SBUF and RB8. The signal to set RI and load SBUF and RB8 will be generated if, and only if, the following conditions are satisfied at the instance when the final shift pulse is generated: • • Either SM2 = 0 or the received 9th bit is equal to 1 RI = 0 If both conditions are met, the ninth data bit received goes into RB8, and the first 8 data bits go into SBUF. If one of these conditions is not met, the received frame is lost. One bit time later, whether the above conditions are met or not, the unit goes back to searching for a one to zero transition at the RXD input. Please note that the value of the received Stop bit is unrelated to SBUF, RB8 or RI. ______________________________________________________________________________________________ www.ramtron.com page 22 of 40 VRS51x550/560 The value to write into the TH1 register is defined by the following formula: UART Baud Rates Calculation In Mode 0, the baud rate is fixed and is represented by the following formula: TH1 = 256 - 2SMODx Fosc 32 x 12x (Baud Rate) Mode 0 Baud Rate = Oscillator Frequency 12 In Mode 2, the baud rate depends on the value of the SMOD bit in the PCON SFR. From the formula below, we can see that if SMOD = 0 (which is the value on reset), the baud rate is 1/32 the oscillator frequency. It is possible to use Timer 1 in 16-bit mode to generate the baud rate for the serial port. To do this, leave the Timer 1 interrupt enabled, configure the timer to run as a 16-bit timer (high nibble of TMOD = 0001B) and use the Timer 1 interrupt to perform a 16-bit software reload. This can achieve very low baud rates. Generating Baud Rates with Timer 2 Timer 2 is often preferred to generate the baud rate, as it can be easily configured to operate as a 16-bit timer with auto-reload. This enables much better resolution than if using Timer 1 in 8-bit auto-reload mode. The baud rate using Timer 2 is defined as: Mode 2 Baud Rate = 2 SMOD x (Oscillator Frequency) 64 The Timer 1 and/or Timer 2 overflow rate determines the baud rates in modes 1 and 3. Generating Baud Rates with Timer 1 When Timer 1 functions as a baud rate generator, the baud rate in modes 1 and 3 are determined by the Timer 1 overflow rate. Mode 1, 3 Baud Rate = Timer 2 Overflow Rate 16 Mode 1, 3 Baud Rate = 2SMODx Timer 1 Overflow Rate 32 The timer can be configured as either a timer or a counter in any of its three running modes. In typical application, it is configured as a timer (C/T2 is set to 0). To make the Timer 2 operate as a baud rate generator the TCLK and RCLK bits of the T2CON register must be set to 1. The baud rate generator mode is similar to the autoreload mode in that an overflow in TH2 causes the Timer 2 registers to be reloaded with the 16-bit value in registers RCAP2H and RCAP2L, which are preset by software. However, when Timer 2 is configured as a baud rate generator, its clock source is Osc/2. Timer 1 must be configured as an 8-bit timer (TL1) with auto-reload with TH1 value when an overflow occurs (Mode 2). In this application, the Timer 1 interrupt should be disabled. The two following formulas can be used to calculate the baud rate and the reload value to be written into the TH1 register. Mode 1, 3 Baud Rate = 2SMODx Fosc 32 x 12(256 – TH1) ______________________________________________________________________________________________ www.ramtron.com page 23 of 40 VRS51x550/560 The following formula can be used to calculate the baud rate in modes 1 and 3 using the Timer 2: Modes 1, 3 Baud Rate = Oscillator Frequency 32x[65536 – (RCAP2H, RCAP2L)] The formula below is used to define the reload value to write into the RCAP2h, RCAP2L registers to achieve a given baud rate. (RCAP2H, RCAP2L) = 65536 - Fosc 32x[Baud Rate] In the above formula, RCAP2H and RCAP2L are the content of RCAP2H and RCAP2L taken as a 16-bit unsigned integer. Note that a rollover in TH2 does not set TF2, and will not generate an interrupt. Because of this, the Timer 2 interrupt does not have to be disabled when Timer 2 is configured in baud rate generator mode. Also, if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not cause a reload from RCAP2x to Tx2. Therefore, when Timer 2 is used as a baud rate generator, T2EX can be used as an extra external interrupt. Furthermore, when Timer 2 is running (TR2 is set to 1) as a timer in baud rate generator mode, the user should not try to read or write to TH2 or TL2. When operating under these conditions, the timer is being incremented every state time and the results of a read or write command may be inaccurate. The RCAP2 registers, however, may be read but should not be written to, because a write may overlap a reload operation and generate write and/or reload errors. In this case, before accessing the Timer 2 or RCAP2 registers, be sure to turn the timer off by clearing TR2. ______________________________________________________________________________________________ www.ramtron.com page 24 of 40 VRS51x550/560 Interrupts The VRS51x550/560 devices have 8 interrupts (9 if we include the WDT) and 7 interrupt vectors (including reset) used for handling. The interrupt can be enabled via the IE register shown below: T ABLE 19: IEN0 INTERRUPT E NABLE REGISTER –SFR A8H Interrupt Vectors The following table specifies each interrupt source, its flag and its vector address. T ABLE 20: INTERRUPT VECTOR CORRESPONDING FLAGS ANS VECTOR ADDRESS Interrupt Source RESET (+ WDT) INT0 Timer 0 INT1 Timer 1 Serial Port Timer 2 Flag WDRESET IE0 TF0 IE1 TF1 RI+TI TF2+EXF2 7 EA 6 - 5 ET2 4 ES 3 ET1 2 EX1 1 ET0 0 EX0 Bit 7 Mnemonic EA Description Disables All Interrupts 0: no interrupt acknowledgment 1: Each interrupt source is individually enabled or disabled by setting or clearing its enable bit. Reserved Timer 2 Interrupt Enable Bit Serial Port Interrupt Enable Bit Timer 1 Interrupt Enable Bit External Interrupt 1 Enable Bit Timer 0 Interrupt Enable Bit External Interrupt 0 Enable Bit Vector Address 0000h 0003h 000Bh 0013h 001Bh 0023h 002Bh External Interrupts The VRS51x550 and the VRS51x560 have two external interrupt inputs named INT0 and INT1. These interrupt lines are shared with P3.2 and P3.3. The bits IT0 and IT1 of the TCON register determine whether the external interrupts are level or edge sensitive. If ITx = 1, the interrupt will be raised when a 1 to 0 transition occurs at the interrupt pin. For the interrupt to be noticed by the processor, the duration of the sum high and low condition must be at least equal to 12 oscillator cycles. If ITx = 0, the interrupt will occur when a logic low condition is present on the interrupt pin. 6 - 5 4 3 2 1 0 ET2 ES ET1 EX1 ET0 EX0 The following figure illustrates the various interrupt sources on the VRS51x550/560. FIGURE 21: INTERRUPT SOURCES INT0 IT0 IE0 TF0 The state of the external interrupt, when enabled, can be monitored using the flags, IE0 and IE1 of the TCON register that are set when the interrupt condition occurs. In the case where the interrupt was configured as edge sensitive, the associated flag is automatically cleared when the interrupt is serviced. If the interrupt is configured as level sensitive, then the interrupt flag must be cleared by the software. INT1 IT1 IE1 INTERRUPT SOURCES TF1 T1 RI TF2 EXF2 ______________________________________________________________________________________________ www.ramtron.com page 25 of 40 VRS51x550/560 Timer 0 and Timer 1 Interrupt Both Timer 0 and Timer 1 can be configured to generate an interrupt when a rollover of the timer/counter occurs (except Timer 0 in Mode 3). The TF0 and TF1 flags serve to monitor timer overflow occurring from Timer 0 and Timer 1. These interrupt flags are automatically cleared when the interrupt is serviced. Execution of an Interrupt When the processor receives an interrupt request, an automatic jump to the desired subroutine occurs. This jump is similar to executing a branch to a subroutine instruction: the processor automatically saves the address of the next instruction on the stack. An internal flag is set to indicate that an interrupt is taking place, and then the jump instruction is executed. An interrupt subroutine must always end with the RETI instruction. This instruction allows users to retrieve the return address placed on the stack. The RETI instruction also allows updating of the internal flag, which will take into account an interrupt with the same priority. Timer 2 Interrupt A Timer 2 interrupt can occur if TF2 and/or EXF2 flags are set to 1 and if the Timer 2 interrupt is enabled. The TF2 flag is set when a rollover of the Timer 2 Counter/Timer occurs. The EXF2 flag can be set by a 1 to 0 transition on the T2EX pin by the software. Note that neither flag is cleared by the hardware upon execution of the interrupt service routine. The service routine may have to determine whether it was TF2 or EXF2 that generated the interrupt. These flag bits will have to be cleared by the software. Every bit that generates interrupts can either be cleared or set by the software, yielding the same result as when the operation is done by the hardware. In other words, pending interrupts can be cancelled and interrupts can be generated by the software. Interrupt Enable and Interrupt Priority When the VRS51x550/560 are initialized, all interrupt sources are inhibited by the bits of the IE register being reset to 0. It is necessary to start by enabling the interrupt sources that the application requires. This is achieved by setting bits in the IE register, as discussed previously. This register is part of the bit addressable internal RAM. For this reason, each bit can be modified individually with one instruction without having to modify the other bits of the register. All interrupts can be inhibited by setting EA to 0. The order in which interrupts are serviced is shown in the following table: T ABLE 21: INTERRUPT NATURAL PRIORITY Serial Port Interrupt The serial port can generate an interrupt upon byte reception or once the byte transmission is complete. Those two conditions share the same interrupt vector and it is up to the user-developed interrupt service routine software to ascertain the cause of the interrupt by examining the serial interrupt flags RI and TI. Note that neither of these flags is cleared by the hardware upon execution of the interrupt service routine. The software must clear these flags. Interrupt Source RESET + WDT (Highest Priority) IE0 TF0 IE1 TF1 RI+TI TF2+EXF2 (Lowest Priority) ______________________________________________________________________________________________ www.ramtron.com page 26 of 40 VRS51x550/560 Modifying the Interrupt Order of Priority The VRS51x550 and VRS51x560 devices allow users to modify the natural priority of the interrupts. One may modify the order by programming the bits in the IP (Interrupt Priority) register. When any bit in this register is set to 1, it gives the corresponding source a greater priority than interrupts coming from sources that don’t have their corresponding IP bit set to 1. The IP register is represented in the table below: T ABLE 22: IP INTERRUPT PRIORITY REGISTER –SFR B8H The WDT timeout delay can be adjusted by configuring the clock divider input for the time base source clock of the WDT. To select the divider value, bit2-bit0 (WDPS2~WDPS0) of the WDTCON should be set accordingly. Clearing the WDT is accomplished by setting the CLR bit of the WDTCON to 1. This action will clear the contents of the 16-bit counter and force it to restart. Watchdog Timer Registers 0 EX0 7 EA 6 - 5 ET2 4 ES 3 ET1 2 EX1 1 ET0 Bit 7 6 Mnemonic - Description 5 4 3 2 1 0 PT2 PS PT1 PX1 PT0 PX0 Gives Timer 2 Interrupt Higher Priority Gives Serial Port Interrupt Higher Priority Gives Timer 1 Interrupt Higher Priority Gives INT1 Interrupt Higher Priority Gives Timer 0 Interrupt Higher Priority Gives INT0 Interrupt Higher Priority Three registers of the VRS51x550/560 devices are associated with the watchdog timer: WDTCON, the WDTLOCK and the SYSCON registers. The WDTCON register allows the user to enable the WDT, to clear the counter and to divide the clock source. The WDRESET bit of the SYSCON register indicates whether the watchdog timer has caused the device reset. T ABLE 23: WATCHDOG T IMER REGISTERS: WDTCON – SFR 9FH 7 WDTE Bit 7 6 5 [4:3] 2 1 0 6 Unused Mnemonic WDTE Unused WDCLR Unused 5 WDCLR 4 3 Unused 2 1 0 WDTPS [2:0] Watchdog Timer The watchdog timer (WDT) is a 16-bit free-running counter that generates a reset signal if the counter overflows. The WDT is useful for systems that are susceptible to noise, power glitches and other conditions that can cause the software to go into infinite dead loops or runaways. The WDT function gives the user software a recovery mechanism from abnormal software conditions. The watchdog timer on the VRS51x550/560 is driven by the oscillator. To enable the WDT, the user must set bit 7 (WDTE) of the Watchdog Timer Control Register (WDTCON) to 1. Once WDTE has been set to 1, the 16-bit counter will start to count with the selected time base source clock configured in WDPS2~WDPS0. The watchdog timer will generate a reset signal if an overflow has taken place. The WDTE bit will be cleared to 0 automatically when the device is reset by either the hardware or a WDT reset. Once the WDT is enabled, the user software must clear it periodically. In the case where the WDT is not cleared, its overflow will trigger a reset of the device. Description Watchdog Timer Enable Bit Watchdog Timer Counter Clear Bit Watchdog Timer Clock Source Divider WDPS [2:0] The user should check the WDRESET bit of the SYSCON register whenever an unpredicted reset has taken place. ______________________________________________________________________________________________ www.ramtron.com page 27 of 40 VRS51x550/560 The table below shows examples of watchdog timeout periods that the user will obtain for different values of the WDPSx bits of the watchdog timer register. T ABLE 24: WATCH DOG T IMER PERIOD VS. WDWDPS [2:0] BIT Crystal Consideration The crystal connected to the VRS51x550/560 oscillator input should be of a parallel type, operating in fundamental mode. The following table shows the value of the capacitors and feedback resistor that must be used at different operating frequencies. XTAL C1 C2 R XTAL C1 C2 R 3MHz 30 pF 30 pF open 33MHz 5 pF 5 pF 6.8K 6MHz 30 pF 30 pF open 40MHz 2 pF 2 pF 4.7K 12MHz 30 pF 30 pF open 16MHz 30 pF 30 pF open 25MHz 15 pF 15 pF 62KO WDPS [2:0] Fosc Division Factor WDT Timeout (ms) @ 20MHz 000 001 010 011 100 101 110 111 8 16 32 64 128 256 512 1024 26.2 52.4 104.8 209.7 419.4 838.8 1677.7 3355.4 The System Control Register The system control register is used to monitor the status of the watchdog timer and inhibit the address Latch Enable signal output. T ABLE 25: T HE SYSTEM CONTROL REGISTER (SYSCON)–SFR BFH Note: Oscillator circuits may differ with different crystals or ceramic resonators in higher oscillation frequency. Crystals or ceramic resonator characteristics vary from one manufacturer to the other. The user should review the technical literature provided with any crystal or ceramic resonators or contact the manufacturer to select the appropriate values for external components. 7 WDRESET 6 5 4 Unused 3 2 1 XRAME 0 ALEI Bit 7 [6:3] 2 1 0 Mnemonic WDRESET Unused Unused Unused ALEI Description Watchdog Timer Reset Status Bit 1: Enable Electromagnetic Interference Reducer 0: Disable Electromagnetic Interference Reducer XTAL1 XTAL VRS51x550 VRS51x560 XTAL2 The WDRESET bit of the SYSCON register is the watchdog timer reset bit. It will be set to 1 when a reset signal is generated by the WDT overflow. The user should check the WDRESET bit state if a reset has taken place in applications where the watchdog timer is activated. R C1 C2 Reduced EMI Function The VRS51x550 and VRS51x560 devices can also be set up to reduce EMI (electromagnetic interference) by setting bit 0 (ALEI) of the SYSCON register to 1. This function will inhibit the Fosc/6Hz clock signal output to the ALE pin. ______________________________________________________________________________________________ www.ramtron.com page 28 of 40 VRS51x550/560 Operating Conditions T ABLE 26: OPERATING CONDITIONS Symbol TA TS VCC5V VCC3V Fosc 25 Description Operating temperature Storage temperature Supply voltage Supply voltage Oscillator Frequency Min. -40 -55 4.5 3.0 3.0 Typ. 25 25 5.0 3.3 - Max. 85 155 5.5 3.6 40 Unit ºC ºC V V MHz Remarks Ambient temperature operating 5 Volt device 3.3 Volt device For 5V & 3.3V application DC Characteristics T ABLE 27: DC CHARACTERISTICS AMBIENT T EMPERATURE = -40°C TO 85°C, 3.0V TO 5.5V Symbol VIL1 VIL2 VIH1 VI H2 VOL1 VOL2 VOH1 VOH2 IIL Parameter Input Low Voltage Input Low Voltage Input High Voltage Input High Voltage Output Low Voltage Output Low Voltage Output High Voltage Output High Voltage Logical 0 Input Current Logical Transition Current Input Leakage Current Reset Pull-Down Resistance Pin Capacitance Valid P o r t 0,1,2,3,4,#EA RES, XTAL1 P o r t 0,1,2,3,4,#EA RES, XTAL1 Port 0, ALE, #PSEN P o r t 1,2,3,4 Port 0 Port 1,2,3,4,ALE,#PSEN P o r t 1,2,3,4 P o r t 1,2,3,4 P o r t 0, #EA RES Min. -0.5 0 2.0 70% VCC Max. 0.8 0.8 VCC+0.5 VCC+0.5 0.45 0.45 2.4 90% VCC 2.4 90% VCC -75 -650 +10 50 300 10 15 10 Unit V V V V V V V V V V uA uA uA Kohm pF mA mA mA mA uA Test Conditions IOL=3.2mA IOL=1.6mA IOH=-800uA (Vcc = 5V) IOH=-80uA IOH=-60uA (Vcc = 5V) IOH=-10uA Vin=0.45V Vin=2.OV 0.45V