VXI VT1433B - Manual (Page 47)

Multiple-module/mainframe Measurements
Grouping of Channels/Modules
The interface library for the VT1433B is designed to allow programming of
several channels from one or several distinct modules, as if they were one entity.
Each VT1433B module has up to eight channels. The library may control up to
a maximum of 255 VT1433B 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).
VT1433B User's Guide
Using the VT1433B
3-9