HP VXI E1432A - Manual (Page 88)

One module of the set of modules needs to be set to output the sync pulse.
Tthe module with the lowest VXI logical address is called the “system
module” and assigned this duty. This can be set with the
e1432_set_multi_sync function call, using the lowest channel ID in the
group (NOT the group ID).
All modules except the “system module” need to be set to use the VXI TTL
trigger lines as the clock source. Use e1432_set_clock_source for this.
Set the “system module” to output the clock. Use e1432_set_clock_master
for this. After this is done, all system sync pulses come from the “system
module” and drive the measurement state machines on all boards in the
group.
Possible Trigger Line Conflict
The following describes a scenario where HP E1432A modules might conflict
and prevent a proper measurement. The conditions allowing the conflict
are complex but must be understood by the user.
After a measurement has completed, the modules are left set up. If a
module (call it module ‘A’) is driving the TTL trigger lines and a different
group is started which also drives the TTL trigger lines (and that different
group does not include module ‘A’), then module ‘A’ will conflict and
prevent the other group from functioning. In this case make a call to
e1432_finish_measure (using the old group ID which includes ‘A’) to turn
off module ‘A’ and allow the new group to function.
Note that if the new group includes all modules of the old group, the
conflict will not occur since e1432_init_measure will reset all modules as
needed. Also note that single module groups do not drive the TTL trigger
lines, so single modules groups are immune from causing or receiving this
conflict.
HP E1432A User's Guide
The C-Language Host Interface Library
4-13
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