VTI Instruments Ametek EX1200A Series, User Manual

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EX1200A Series Basic Mainframe Operation 69
In addition to a single-master/multiple-slaves configuration, the Trigger Bus can be configured in
Wired-OR mode. This mode allows multiple instruments to bring an LXI Trigger Bus channel to a
“1” state. The channel will only go back to “0” when all in
struments have released it. This is
useful if multiple instruments in parallel operation must all complete before another instrument
can begin its operations. Each channel is programmable as to whether it is in Wired-OR or Master-
Slave mode.
When an Trigger Bus channel is configured for Wired-OR mode, exactly one instrument on the
bus must provide a bias on the channel. This is what allows the channel to fall deterministically
back to a “0” state when all other devices release it. Each channel is progra
mmable as to whether
it will provide the Wired-OR Bias when it is in Wired-OR mode. The default selections are:

Wired-OR mode is off

Wired-OR Bias mode is off
DMM Front Panel Connectors (Optional)
These connections allow for use of the onboard DMM in measurements. The DMM and its
connections are further discussed in Section 4.
DMM Bus I/O
For EX1200A mainframes with a DMM, it is possible to access the DMM through the DMM bus
as an alternative to the front panel banana jacks (see
DMM Input Connections in Section 4 for
more detail on the DMM front panel connector). Alternatively, the bus can be used to route signals
to an external DMM though this connector. To use the onboard DMM, the DMM inputs must be
assigned to the backplane instead of the front panel. Please see the
Matrix Bus description below
for a description of the bus signals.
Pin Function
1 +SHI
2
N/C
3
+HI
4 N/C
5 +DAMPS
6
-SLO
7 GUARD
8 -LO
9
N/C
T
ABLE
3-5: DMM B
US
I/O P
IN
S
IGNALS
Reset Button
A reset button is accessible through a hole in the rear panel of the EX1200A and can be used to
restore default switch and network settings. This is useful for recovering from an incorrect or
unknown network configuration. There are three modes of operation for this button which are
based on the time the reset button is depressed. The reset is implemented according to the LXI
LAN Configuration Initialize (LCI) Mechanism specification.
Debounce Protection Mode
To prevent unintentional resets of the EX1200A, there is a debounce protection mechanism. If the
reset button is depressed for less than 1 s, the activation of the reset button is treated as
unintentional and no action is taken.
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