ASEM CPU 1021/A - Summary of Commands

CPU 1021/A User’s Guide
10 Asem S.p.A.
3. Run
waiting for command out 566h=nh (0<n<=FFh), to refresh the
WD, resetting the timer count. If there is no refresh and the timer
expires, it changes to Expired.
4. Expired
after the watch-dog timer has expired:
• the watch-dog LED on the CPU 1021/A will come on
• bit 0 of the port I/O 568h (watch-dog in Expired state) will be
set to logic state 1. The application software will
subsequently be able to read it.
• There will then be generated a Reset, based on the settings
made by the user.
To change back from Expired state to Idle it is necessary:
- To set logic state 0 for bit 0 of port 568h
- To set logic state 0 for the 8 bits of port 566h
To turn off the watch-dog LED it is necessary to press Reset watch-
dog button.
Summary of commands
The watch-dog is capable of receiving the following commands from
the application software:
Command
Effect
out 565h, 80h
Changes the watch-dog from Idle state to Set
out 566h, nh (0<n<=FFh)
Switches state "Set" to "Run" and also must be
periodically issued while the WD is in a state of
"Run" to make a refreshing and avoid the time-out.
out 568h, 0h
converts the bit 0 of port 568h to 0 (zero bit
indicates that WD Expired)
out 566h, 0h
Goes from "Expired" to "Idle" and is ready to be
rearmed.
The addresses of I / O mentioned refer to the programming carried
by the version of BIOS 8921965A.04. To obtain the values
programmed by earlier versions add 180h to any address.