Teknor Industrial Computers TEK-CPCI-1000, Technical Reference Manual

Page: 32 / 141

TEK-CPCI-1000 Technical Reference Manual
6-10
6.6.2 Power Fail Monitoring
A power failure condition may be detected if a low backup battery condition occurs, or a +5V
monitored power supply (user defined) falls below 4.75V.
When power failure is enabled, a power failure condition is detected if either of the two
above conditions occurs. To enable power fail monitoring, the W9 jumper cap must be
installed.
To select wheter to monitor the low battery or the user defined power supply voltage, use the
W11 jumper.
Jumper location and configuration are described in Section 10 - Setting Jumpers.
6.6.3 Watchdog
The watchdog is used to monitor the CPU inactivity. After a specified duration of inactivity,
the CPU will be reset.
To generate a RESET when the watchdog times out, use the W10 jumper.
Working with the Watchdog
The watchdog must be enabled and refreshed by software. To enable the watchdog by
software, first write "1" in the bit 0 of the I/O Register #1 (see Section 6.6.1 - Supervisor I/O
Registers).
When enabled, the watchdog must be refreshed by the processor by writing alternatively "0"
and "1" to the bit 1 of the I/O Register #1, once every 1.6 seconds to verify proper software
execution. If a hardware or software failure occurs such that the watchdog is not refreshed, a
reset pulse is generated by the watchdog to restart the processor.
Following a reset, the watchdog is always disabled.
CAUTION
The user program must first configure the I/O Register #1 (set at base
the address 190h, 290h or 390h, according to the W3 jumper setting),
and must also include a refresh routine. Be certain to keep a mirror
image of this register when programming it. This is necessary since the
register is a write-only user register and, as a result, is not used by the
system BIOS.