HP VXI E1432A - Manual (Page 48)

Multiple-module/mainframe Measurements
Grouping of Channels/Modules
The interface library for the HP E1432A is designed to allow programming
of several channels from one or several distinct modules, as if they were
one entity. Each HP E1432A module has up to 16 channels. The library
may control up to a maximum of 255 HP E1432A modules (8160 channels).
The function hpe1432_createChannelGroup can be used to declare any
number of groups of channels, possibly overlapping. Each group can be
uniquely identified by a group ID.
The ‘target’ of a library function is either a channel, a group, or (rarely) a
module, depending on the nature of the call. When the same library
function may be called with either a channel or a group identifier, its
‘target’ is shown by a parameter named ID.
Multiple-module Measurements
A channel group that spans more than one module will need to be
configured to use the TTL trigger lines on the VXI Bus for inter-module
communications. This configuration is automatically performed in the
hpe1432_initMeasure call unless defeated using hpe1432_setAutoGroupMeas.
The following discussion outlines what hpe1432_initMeasure does
automatically. This must be done by the user if
hpe1432_setAutoGroupMeas has been used to defeat auto configuration.
There are eight VXI TTL trigger lines that can be used for multi-module
synchronization. Often, these lines are used in pairs, one for sample clock
and one for Sync/Trigger. The hpe1432_setTtltrgLines function selects
which TTL trigger lines to use; this function always uses the TTL trigger
lines in pairs. Calling hpe1432_setClockSource with the group ID will set
all modules to the same pair.
All modules need to be set to use the shared sync line rather than the
default setting of internal sync. This can be done with the
hpe1432_setMultiSync function, using the group ID.
One module of the set of modules needs to be set to output the sync pulse.
The module with the lowest VXI logical address is called the “system
module” and is assigned this duty. This can be set with the
hpe1432_setMultiSync function call, using the lowest channel ID in the
group (NOT the group ID).
HP E1432A User's Guide
Using the HP E1432A
3-9
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