Rainbow-electronics DS12C887 Manual de usuario Pagina 1

1 of 19 020900FEATURES Drop-in replacement for IBM AT computerclock/calendar Pin compatible with the MC146818B andDS1287 Totally nonvolatile wit

DS12C88710 of 19CENTURY REGISTERThe century register at location 32h, is a BCD register designed to automatically load the BCD value 20as the year reg

DS12C88711 of 19OSCILLATOR CONTROL BITSWhen the DS12C887 is shipped from the factory, the internal oscillator is turned off. This featureprevents the

DS12C88712 of 19UPDATE CYCLEThe DS12C887 executes an update cycle once per second regardless of the SET bit in Register B. Whenthe SET bit in Register

DS12C88713 of 19ABSOLUTE MAXIMUM RATINGS*Voltage on Any Pin Relative to Ground -0.3V to +7.0VOperating Temperature 0° to 70°CStorage Temperature -40°C

DS12C88714 of 19AC ELECTRICAL CHARACTERISTICS (0°C to 70°C; VCC = 5.0V ± 10%)PARAMETER SYMBOL MIN TYP MAX UNITS NOTESCycle Time tCYC385 DC nsPulse Wid

DS12C88715 of 19OUTPUT LOAD Figure 4DS12C887 BUS TIMING FOR MOTOROLA INTERFACE

DS12C88716 of 19DS12C887 BUS TIMING FOR INTEL INTERFACE WRITE CYCLEDS12C887 BUS TIMING FOR INTEL INTERFACE READ CYCLE

DS12C88717 of 19DS12C887 IRQ RELEASE DELAY TIMINGPOWER DOWN / POWER UP TIMING

DS12C88718 of 19POWER DOWN / POWER UP TIMINGPARAMETER SYMBOL MIN TYP MAX UNITS NOTESCS at VIH before Power-DowntPD0µsVCC slew from 4.5V to 0V(CS at

DS12C88719 of 19DS12C887 REAL TIME CLOCK PLUS RAMNOTE:Pins 2, 3, 16, 20, 21 and 22 are missing by designPKG 24-PINDIM MIN MAXA INMM1.32033.531.33533.9

DS12C8872 of 19OPERATIONThe block diagram in Figure 1 shows the pin connections with the major internal functions of theDS12C887. The following parag

DS12C8873 of 19R/ W (Read/Write Input) – The R/ W pin also has two modes of operation. When the MOT pin isconnected to VCC for Motorola timing, R/W

DS12C8874 of 19DS12C887 BLOCK DIAGRAM Figure 1

DS12C8875 of 19POWER-DOWN/POWER-UP CONSIDERATIONSThe Real Time Clock function will continue to operate and all of the RAM, time, calendar, and alarmme

DS12C8876 of 19TIME, CALENDAR AND ALARM LOCATIONSThe time and calendar information is obtained by reading the appropriate memory bytes. The time,calen

DS12C8877 of 19CONTROL REGISTERSThe DS12C887 has four control registers which are accessible at all times, even during the update cycle.REGISTER AMSB

DS12C8878 of 19REGISTER BMSB LSBBIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0SET PIE AIE UIE SQWE DM 24/12 DSESET - When the SET bit is a 0, the u

DS12C8879 of 19REGISTER CMSB LSBBIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0IRQF PF AF UF 0 0 0 0IRQF - The Interrupt Request Flag (IRQF) bit is s