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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).
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, it’s
‘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.
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
e1432_set_multi_sync function, using the group ID.
HP E1432A User's Guide
The C-Language Host Interface Library
4-12