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Real time clock in powerpoint7/27/2023 ![]() Ten clock/calendar bytes Current seconds 0x0 0x1 0x2 0x3 0x4 0x5 0圆 0x7 0x8 0x9 Range is 0.59 Range is 0.59 Range is 0.59 Range is 0.59 Range is 0.23 or 1.12 Range is 0.23 or 1.12 Range is 1.7 (Sunday=1) Range is 1.31 Range is 1.12 (January=1) Range is 0.99 Alarm seconds Current minutes Alarm minutes Current hours Alarm hours Day-of-the-Week Date of the Month Current Month Current Year A system quirk: The most significant bit at port 0x70 is used to control a gate that can ‘mask’ the Non-Maskable Interrupt circuitry.The RTC interfaces with system software as an array of 128 bytes, accessed via i/o ports 0x70 and 0x71 using a multiplexing scheme: port 0x70: address-port port 0x71: data-port.Provides 114 bytes of nonvolative storage.Counts seconds, minutes, hours, days, day-of-the-week, date, month, and year (with leap-year compensation), valid up until the year 2100 AD, with options for 12/24-hour clock and Daylight Savings. ![]() ![]() Can operate over ten years without power.You can also get the Motorola datasheet (by writing to its corporate headquarters).Its capabilities are described online in an official datasheet by Dallas Semiconductor (see ‘Maxim’ integrated circuit: DS12887).Other companies have ‘cloned’ this chip.PC-AT’s Real-Time Clock plus RAM was manufactured by Motorola Corporation.It also provided a small amount of memory which could retain configuration settings.A special battery-powered peripheral was added to keep track of the time and date.This defect was eliminated in the IBM-AT.Users had to run a utility program to reset the date and time after any system reboot.The original IBM-PC had no internal clock.The PC’s Real-Time Clock An introduction to the capabilities and programming of the Real-Time Clock and CMOS memory
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