User Guide

10 Documentation Number ATxWDT-1303
B&B Electronics Mfg Co – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
B&B Electronics Ltd – Westlink Comm. Pk – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]
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
ATRWDTthefifthbitistheresetflag.Itwillbea1whenthe
ATRWDTresetsthecomputeranda0ifthecomputerhasnotbeen
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
XFORATX
XX
XX
XX
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.