TS-5300 User’s Manual
Technologic Systems
05/21/09
16
10 Real Time Clock
The Dallas Semiconductor DS12887 is used for the PC compatible battery-backed real-time clock. It is
a completely self-contained module that includes a Motorola 146818 compatible clock chip, the 32.768
kHz crystal, the lithium battery, and 114 bytes of battery-backed CMOS RAM. It is guaranteed to
maintain clock operation for a minimum of 10 years in the absence of power. It is located at the standard
PC I/O addresses of Hex 070 and 071. The top 48 bytes (index 50h through 7Fh) are not used by the
BIOS and are available for user applications.
The RTC is capable of generating a square wave output function with a period of 500 mSec to 122
uSec. The square wave output pin is connected to IRQ8 on the processor, and can be used to generate
periodic interrupts. The keypad example code uses this function to generate interrupts at a 256 Hz rate.
ftp://ftp.embeddedarm.com/old/downloads/KEYPAD.ZIP
Summary of Contents for TS-5300
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