ICS PCI-WDT 500, Руководство по эксплуатации продукта

Страница: 25 / 44

Manual Number: 00650-144-1 Page 16
PCI-WDT 500/501 Manual
Computer Temperature Monitor
On the PCI-WDT 501 the temperature inside the computer can be read using an 8-bit register at
BASE+5. To convert the byte read into temperature in Fahrenheit, multiply the value read by 11/15
and then add 7.
Interrupts
The card is capable of generating interrupts for a variety of reasons. If any or all of the features
described on page 7 are installed (as well as the watchdog-timeout-near warning), they can be read
from the Status Register at BASE+4. Bit assignments are as listed below. An interrupt is also
generated upon a digital input’s change-of-state—if that option is installed.
Status Register
Bit assignments of the Status Register (Base A4) are as follows:
BD0 Watchdog counter refresh reminder (Active low)
BD1 Temperature good (Active high)
BD2 Isolated Input #0 status (Same as input)
BD3 Isolated Input #1 status (Same as input)
BD4 Fan good (Active high)
BD5 Power Supply overvoltage (Active low)
BD6 Power Supply undervoltage (Active low)
BD7 IRQ generated (Active high)
Watchdog Programming Options
Programming PCI-WDT50x is straightforward. Counters 0 and 1 of the type 8254 counter/timer
are concatenated and operate as a 32-bit down counter to provide the time delay before a timeout
occurs. A special register provides enable and disable functions for the counters and, thus, the
watchdog itself. Writing any value to the register located at base a7 enables the counters to
count. Reading the register disables the counters and stops the watchdog.
To program the watchdog interval:
a. Disable the counters.
b. Program the counters with the desired time delays.
c. Enable the counters.
Once the counters have been enabled, the computer will reset if the 32-bit counter decrements all
the way to zero.