
12
FN1547.8
October 29, 2007
Alarm
The output of the alarm comparator is enabled when this bit
is set high. When a comparison occurs between the
seconds, minutes and hours time and alarm counters, the
interrupt output is activated. When loading the time counters,
this bit should be set low to avoid a false interrupt. This is not
required when loading the alarm counters. See "Functional
Description", INT for explanation of alarm delay on
page 10.Periodic Select
The value in these 4 bits will select the frequency of the
periodic output. (See Table
3).
CLOCK CONTROL REGISTER (Write/Read) - Address 31H
D7
D6
D5
D4
D3
D2
D1
D0
START
LINE
XTAL
50Hz
CLK OUT
SEL
STOP
XTAL
10
60Hz
210
INTERRUPT CONTROL REGISTER (Write/Read) - Address 32H
D7
D6
D5
D4
D3
D2
D1
D0
WATCHDOG
POWER
DOWN
POWER
SENSE
ALARM
PERIODIC SELECT
NOTE: All bits are reset by power-on reset.
TABLE 3. PERIODIC INTERRUPT OUTPUT
D0 - D3 VALUE
PERIODIC INTERRUPT
OUTPUT FREQUENCY
FREQUENCY TIME BASE
XTAL
LINE
0
Disable
1
2048Hz
X
2
1024Hz
X
3
512Hz
X
4
256Hz
X
5
128Hz
X
6
64Hz
X
50Hz or 60Hz
X
7
32Hz
X
8
16Hz
X
98Hz
X
10
4Hz
X
11
2Hz
X
12
1Hz
X
13
Minute
X
14
Hour
X
15
Day
X
CDP68HC68T1