B&B Electronics PC Watchdog Timer Card ATRWDT - Manual (Page 12)

10 Documentation Number ATxWDT-1303
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The four bit latch values are also readable. Reading these bits is
recommended to verify the presence and setup of the WDT. The
BASIC command INP <WDTaddress> is used to read from the
WDT. The top three bits are not used and can be masked out. In the
ATRWDT the fifth bit is the reset flag. It will be a 1 when the
ATRWDT resets the computer and a 0 if the computer has not been
reset by the ATRWDT. This bit will be cleared if the computer is
turned off or after the bit has been read. A small example program,
written in QuickBASIC can be found in Appendix B.
Table 4. Registers
Write Register Read Register
L0 L0
L1 L1
L2 L2
L3 L3
X Reset Flag FOR ATR
X FOR ATX
X X
X X
X X
X = Don’t Care
Pinouts
Three pins of the male DB-9 connector are used for the WDT.
Pins 4 and 7 are the external device reset relay contacts. These are
non-polarized, normally open contacts, and pins 3 and 7 are for the
normally closed.
Figure 2 is a schematic of the output portion of the WDT.