Technical information

Read This First. OPTO DIO Reference
interrupt or reset signal is generated on timeout. Reading the
watchdog register refreshes the timer, postponing timeout for 50
milliseconds. When the watch dog times out an timer expired
output signal is set. On those cards that provide opto isolated
outputs the watchdog timer expired output, in place of Port A
line bit 0, is available on the 50 way edge connector.
The watch dog timer expired output is jumper selectable to one
of four options.
Timer expired jumper selectable output signal options are:-
i) a constant high level voltage.
ii) a constant low level voltage.
iii) a goes high then returns low pulse.
iv) a goes low then returns high pulse.
The constant level pulses are suitable as enable lines for stepper
motors or switches etc.
The goes high then returns low pulse is suitable for gating onto
PC interrupt and reset lines. Note many PC reset lines are
outputs only and so the opto cards watchdog pulse will not cause
a PC reset on timeout.
The watch dog is enable by writes to the watchdog register. See
Figure 1-13.
Figure 1-13. Watch Dog Enable Register.____________________________________
WATCH DOG ENABLE REGISTER DEFAULT ADDR ARE 030B & 030F Hex
THIS IS A READ WRITE REGISTER
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
WRITE DONT CARE GATE GATE GATE GATE
PORT C2 PORT C2 JUMPER JUMPER
READ ALWAYS 0 BIT 3 BIT 0 BUS BUS
TO IRQ TO IRQ TO IRQ TO RESET
READ OF THIS REGISTER REFRESHES THE WATCH DOG TIMER
READ THIS AT LEAST ONCE EVERY 50 MILLI SECONDS TO PREVENT TIMOUT
Note OUT24, OUT48 and DIO16 BIT 3 and BIT 2 ALWAYS = ZERO!
Chapter 1 Page 11