Intel 386 - Manual (Page 497)

Intel386™ EX EMBEDDED MICROPROCESSOR USER’S MANUAL
17-2
READY#). In bus monitor mode, the ADS# signal from the bus interface unit (BIU) reloads the
down-counter and the READY# signal stops it. The READY# signal can be generated either ex-
ternally or internally, using the WDTRDY bit in the PWRCON register (Figure 17-5). If this bit
is deasserted, then an external READY# is required to terminate the cycle when the WDT times
out (WDTOUT is asserted) in Bus Monitor mode. In this case, if a READY# is never generated
by external logic, the processor hangs (since the bus cycle never terminates). If the WDTRDY bit
is set, the processor generates an internal READY# to terminate the cycle upon time-out
(WDTOUT is asserted) in Bus Monitor mode.
The WDT circuitry correctly matches each READY# with a corresponding ADS# (even in pipe-
lined mode when two ADS# pulses occur before the first READY# pulse).
Figure 17-1. Watchdog Timer Unit Connections
E
I
B
u
s
A2330-02
Reload
Registers
WDTRLDH
WDTRLDL
32-Bit
Down Counter
WDTCLR
Connect
to NMI
or RESET
8-State
Binary
Counter
WDTOUT
WDTSTATUS
WDTCNTH
WDTCNTL
WDTOUT#
to IR7 of
Slave 8259A