User manual

Using the Relay Multiplexer 41Chapter 2
To connect the HI and LO terminals of bank 0 channel 0 and the LO terminal
of bank 4 channel 0 to their COM terminals, execute:
FUNC 1,WIRE3
!Configures the multiplexer (card 01) for
three-wire operation
CLOS (@100)
!Connects the HI and LO terminals of bank 0
channel 0 to the bank 0 COM terminals and
the LO terminal of bank 4, channel 0 to the
bank 4 LO COM terminal
NOTE If the Status Register switch is set to three-wire operating mode, the FUNC
1,WIRE3 command is not required. In three-wire mode, banks are paired
0/4, 1/5, 2/6, and 3/7. Do not connect user wiring to the HI terminal in the
upper bank pair (4-7), as this terminal is switched during three-wire
operation. Upper bank pair (4-7) channels cannot be switched or queried
while in this mode.
Example: Switching
Channels (Four-Wire)
This example illustrates four-wire mode operation. The HI and LO terminals
of bank 0 channel 0 are closed, connecting them to the bank 0 COM
terminals. At the same time, the HI and LO terminals of bank 4 channel 0 are
closed, connecting them to the bank 4 COM terminals. Figure 2-4 shows
how the multiplexer is configured.
For four-wire operation, the control relays are set as follows. 0990/0991 
are set open when SCAN <channel_list> is executed. 0992/0993 will close
when SCAN:PORT ABUS is selected during a scan. They are opened
otherwise (see “Scanning Channels”). 0994/0995/0996 are set open when
SCAN <channel_list> is executed.
Figure 2-3. Example: Three-Wire Mode Channel Switching
H
L
COM
L
H
CH0
BANK 0
SWITCH CARD TERMINAL MODULE
H
L
L
H
CH 0996
1 IN
2 IN
1 OUT
2 OUT
ANALOG BUS GUARD
NO CONNECTION
3 IN
NO CONNECTION
3 OUT
BANK 4
COM
CH0
G