53
Watchdog Timer
4
Registers 0 through A are Clock, Calendar, Time of Day Registers.
Register B is the Command Register.
Registers C and D are Watchdog Alarm Registers.
The Watchdog Timer contains 14 registers which are 8-bits wide. These registers
contain all of the Time of Day, Alarm, Watchdog, Control, and Data information. The
Clock Calendar, Alarm, and Watchdog Registers have both external (user accessible)
and internal memory locations containing copies of the data. The external memory
locations are independent of the internal functions except that they are updated
periodically by the transfer of the incremented internal values. Registers 0, 1, 2, 4, 6, 8,
9, and A contain Time of Day and Data information in Binary Coded Decimal (BCD).
Registers 3, 5, and 7 contain the Time of Day Alarm information in BCD. The
Command Register (Register B) contains data in binary. The Watchdog Alarm
Registers are Registers C and D and information stored in these registers is in BCD.
Table 4-6 Watchdog Registers
Register
Address
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Range
0
$500
0.1 Seconds (BCD)
0.01 Seconds (BCD)
00 - 99
1
$501
10 Seconds (BCD)
Seconds (BCD)
00 - 59
2
$502
10 Minutes (BCD)
Minutes (BCD)
00 - 59
3
$503
M
10 Minute Alarm (BCD)
Minute Alarm (BCD)
00 - 59
4
$504
0
12/24
AM/PM
*
10 Hr
Hours (BCD)
5
$505
M
12/24
AM/PM
*
10 Hr
Hour Alarm (BCD)
6
$506
0
0
0
0
Days (BCD)
01 - 07
7
$507
M
0
0
0
Day Alarm (BCD)
01 - 07
8
$508
0
0
10 Date (BCD)
Date (BCD)
01 - 31
9
$509
Eosc
1**
0
10 Mo
Months (BCD)
01 - 12
A
$50A
10 Years (BCD)
Years (BCD)
00 - 99
B
$50B
Te
Ipsw
Ibh/lo
Pu/lvl
Wam
Tdm
Waf
Tdf
C
$50C
0.1 Seconds (BCD)
0.01 Seconds (BCD)
00 - 99
D
$50D
10 Seconds (BCD)
Seconds (BCD)
00 - 99
* In the 12 hour mode bit 5 determines AM (0) or PM (1). In the 24 hour mode bit 5 combines with Bit 4 to
represent the 10 hour value.
** Bit 6 of Register 9 must be set to a 1. If set to a 0, an unused square wave will be generated in the circuit.
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