User`s guide

A
A
R
R
-
-
B
B
1
1
3
3
2
2
0
0
U
U
s
s
e
e
r
r
’
’
s
s
G
G
u
u
i
i
d
d
e
e
3-14
3.15.2 WD REPORT REGISTER - INDEX 38H
This register is used to select the watchdog report when the watchdog times out.
Bit 7-4 Watchdog Timer Time-out Report Signal Select
0000 No output signal
0001 IRQ3 selected
0010 IRQ4 selected
0011 IRQ5 selected
0100 IRQ6 selected
0101 IRQ7 selected
0110 IRQ9 selected
0111 IRQ10 selected
1000 IRQ11 selected
1001 IRQ12 selected
1010 IRQ14 selected
1011 IRQ15 selected
1100 NMI selected
1101 System reset selected
1110 No output signal
1111 No output signal
Bit 3-0 Other function. Please do not modify these bits.
Note 1):If you program the watchdog to generate an IRQ signal when it times out, you should initialize
the IRQ interrupt vector and enable the second interrupt controller (8259 PIC) in order to enable
the CPU to process this interrupt. An interrupt service routine is required too.
2) Before you initial the interrupt vector of the IRQ and enable the PIC, please enable the
watchdog timer previously, otherwise the watchdog timer will generate an interrupt at the time the
watchdog timer is enabled.
3.15.3 WD TIMER COUNTER(24 BITS) - INDEX 39H, 3AH, AND 3BH
These registers are used to set the desired counter for the watchdog to count down. The time
base of each count is 30.5μsec.
INDEX 3Bh 3Ah 39h
Data Bit D7…D0 D7…D0 D7…D0
24-bit Counter D23…D16 D15…D8 D7…D0
For example:
INDEX
3Bh 3Ah 39h
Watchdog Timer
00h 00h 01h
30.5 μsec
00h 00h 02h
61.0 μsec
00h 01h 00h 7.8 m sec
00h 02h 00h 15.6 m sec
01h 00h 00h 2 sec
02h 00h 00h 4 sec
0FFh 0FFh 0FFh 512 sec