DS1543W-120

PRELIMINARY DS1543 64k NV Timekeeping RAM www.dalsemi.com FEATURES








PIN ASSIGNMENT Integrated NV SRAM, real time clock, crystal, power-fail control circuit and lithium energy source Clock registers are accessed identical to the static RAM. These registers are resident in the sixteen top RAM locations Totally nonvolatile with over 10 years of operation in the absence of power Precision Power-On Reset Programmable Watchdog Timer and RTC Alarm BCD coded year, month, date, day, hours, minutes, and seconds with automatic leap year compensation valid up to the year 2100 Battery voltage level indicator flag Power-fail write protection allows for ±10% Vcc power supply tolerance Lithium energy source is electrically disconnected to retain freshness until power is applied for the first time ORDERING INFORMATION DS1543-XXX *DS1543W-XXX (5V) -70 -100 70 ns access 100 ns access (3.3V) -120 120 ns access -150 150 ns access RST A12 A7 A6 A5 A4 A3 A2 A1 A0 DQ0 DQ1 DQ2 GND 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 VCC WE IRQ/FT A8 A9 A11 OE A10 CE DQ7 DQ6 DQ5 DQ4 DQ3 28-Pin Encapsulated Package (700 Mil Extended) PIN DESCRIPTION A0-A12 DQ0-DQ7 IRQ \FT RST CE OE WE VCC GND NC 1 of 17 - Address Input - Data Input/Outputs - Interrupt, Frequency Test Output (Open-Drain) - Power-On Reset Output (Open-Drain) - Chip Enable - Output Enable - Write Enable - Power Supply Input - Ground - No Connection 081000 DS1543 DESCRIPTION The DS1543 is a full-function real-time clock/calendar (RTC) with a RTC alarm, watchdog timer, poweron reset, battery monitor, and 8k x 8 non-volatile static RAM. User access to all registers within the DS1543 is accomplished with a bytewide interface as shown in Figure 1. The RTC registers contain year, month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for day of month and leap year are made automatically. The RTC registers are double-buffered into an internal and external set. The user has direct access to the external set. Clock/calendar updates to the external set of registers can be disabled and enabled to allow the user to access static data. Assuming the internal oscillator is turned on, the internal set of registers are continuously updated; this occurs regardless of external registers settings to guarantee that accurate RTC information is always maintained. The DS1543 has interrupt ( IRQ /FT) and reset ( RST ) outputs which can be used to control CPU activity. The IRQ /FT interrupt output can be used to generate an external interrupt when the RTC register values match user programmed alarm values. The interrupt is always available while the device is powered from the system supply and can be programmed to occur when in the battery backed state to serve as a system wake-up. Either the IRQ /FT or RST outputs can also be used as a CPU watchdog timer, CPU activity is monitored and an interrupt or reset output will be activated if the correct activity is not detected within programmed limits. The DS1543 power-on reset can be used to detect a system power down or failure and hold the CPU in a safe reset state until normal power returns and stabilizes; the RST output is used for this function. The DS1543 also contains its own power fail circuitry which automatically deselects the device when the VCC supply enters an out of tolerance condition. This feature provides a high degree of data security during unpredictable system operation brought on by low VCC levels. PACKAGES The DS1543 is available in two packages (28-pin DIP and 34-pin PowerCap module). The 28-pin DIP style module integrates the crystal, lithium energy source, and silicon all in one package. The 34-pin PowerCap module board is designed with contacts for connection to a separate PowerCap (DS9034PCX) that contains the crystal and battery. This design allows the Power-Cap to be mounted on top of the DS1543P after the completion of the surface mount process. Mounting the PowerCap after the surface mount process prevents damage to the crystal and battery due to the high temperatures required for solder reflow. The PowerCap is keyed to prevent reverse insertion. The PowerCap Module board and PowerCap are ordered separately and shipped in separate containers. The part number for the PowerCap is DS9034PCX. 2 of 17 DS1543 DS1543 BLOCK DIAGRAM Figure 1 DS1543 OPERATING MODES Table 1 VCC In Tolerance VBAT < VCC < Tolerance