VXI VT1433B - Manual (Page 90)

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 16 channels. The library may control up to a
maximum of 255 VT1433B modules (8160 channels).
When initializing the interface library, all module logical addresses are passed in
the call to e1432_assign_channel_numbers. This function associates a logical
channel ID with each channel. From then on, library functions use these logical
IDs rather than the logical address.
The function e1432_create_channel_group 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 automatically performed in the e1432_init_measure call unless
defeated using e1432_set_auto_group_meas.
The following discussion outlines what e1432_init_measure does automatically.
This must be done by the user if e1432_set_auto_group_meas 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 e1432_set_ttltrg_lines function selects which TTL
trigger lines to use; this function always uses the TTL trigger lines in pairs.
Calling e1432_set_clock_source with the group ID will set all modules to the
same pair.
VT1433B User's Guide
The Host Interface Library
4-12