Ziatech Corporation ZT 8809A, Operating Manual, Page: 225 / 412

Chapter 10
REAL-TIME CLOCK (DS 1215)
Contents Page
OVERVIEW
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-1
OPERATION
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-3
TIMECHIP COMPARISON REGISTER DEFINITION
. . . . . . . . . . . . .
10-5
TIMEKEEPER REGISTER INFORMATION
. . . . . . . . . . . . . . . . . . . . . .
10-6
TIMECHIP REGISTER DEFINITION
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-7
AM/PM 12/24-Hour Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-8
Oscillator and Reset Bits
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-8
Zero Bits
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10-8
OVERVIEW
The real-time clock is a combination of CMOS timekeeper and
memory controller, providing protection to a memory device when
power is not within acceptable limits.
The device is a Dallas
Semiconductor DS 1215 that may be battery-backed with an optional
battery mounted on the ZT 8809A. This battery backs up the RAM on
board and maintains the timekeeping operation. A functional diagram
of the timekeeper is shown in Figure 10-1 on page 10-2.
The timekeeper provides hundredths of seconds, seconds, minutes,
hours, day, date, month, and year information. The last date of the
month is automatically adjusted for months with less than 31 days,
including correction for a leap year every four years. The watch
operates in one of two formats: a 12-hour mode with an AM/PM
indicator or a 24-hour mode.
10-1