Pamux User’s Guide 25
The watchdog timeout interval is set within the hardware and cannot be changed by the user. Refer to
Table 2-3 for minimum, typical, and maximum watchdog timeout values.
Table 2-3: Watchdog Timeout Values
Minimum Typical Maximum
1.0 sec 1.6 sec 2.25 sec
Jumpers 7 and 8 (Reset)
One of the control lines on the Pamux bus is the reset line. This line is used for turning off the relays
on all Pamux stations on the bus. Note that the reset is not intended to be used to shut off outputs
upon a system communication error.
Two jumpers control how the reset line affects the B4. Jumper 7 determines the polarity of the reset
line, either active high or active low, as shown in Table 2-4. In general, it does not matter which
polarity you select as long as you are consistent throughout your Pamux system.
Table 2-4: B4 Reset Jumper
Reset Level Jumper 7
Active High In
Active Low Out
Jumper 8 determines how the reset line affects the watchdog timer function of channel 0.
If jumper 8 is not installed, the reset line will not affect the watchdog timer function. Hence, if channel
0 activates due to a watchdog condition, an active reset line will have no effect on channel 0
(although it will deactivate any other channels that are on).
If jumper 8 is installed and the watchdog jumpers are configured to activate channel 0 upon a
timeout, the state of channel 0 depends on whether or not the reset activates before the timeout
occurs:
• If the reset line activates first, all outputs will deactivate. If a subsequent timeout occurs, no
effect will take place until the reset line deactivates, at which time the watchdog function
will take place and channel 0 will activate.
• If the timeout occurs first, the watchdog function takes place and channel 0 activates. If a
subsequent reset occurs, channel 0 will not be affected and will remain active.
TERMINATING A B4 STATION
For stations on a Pamux bus to operate correctly, both ends of the bus must be terminated. The
host computer and the last Pamux station on the bus are the only devices that should be terminated.
Note that if you are using an Opto 22 Pamux adapter card, the host computer is automatically
terminated, since termination resistors are built into the card.
SYSTEM SETUP
To Next Page
Loading...
