HP VXI E1432A - Manual (Page 103)

Host Interrupt Handling
When the HP E1432A asserts the VME interrupt line, SICL will cause the
specified interrupt handler to get called. Typically the interrupt handler
routine will read data from the module, and then re-enable HP E1432A
interrupts with e1432_reenable_interrupt. The call to
e1432_reenable_interrupt must be done unless the host is not interested in
any more interrupts.
Inside the interrupt handler, almost any HP E1432A Host Interface library
function can be called. This works because the Host Interface library
disables interrupts around critical sections of code, ensuring that
communication with the HP E1432A module stays consistent. Things that
are not valid in the handler are:
q Calling e1432_delete_channel_group to delete a group that is simultaneously
being used by non-interrupt-handler code.
q Calling one of the read data functions (e1432_read_raw_data,
e1432_read_float32_data, or e1432_read_float64_data), if the
non-interrupt-handler code is also calling one of these functions.
q Calling e1432_assign_channel_numbers to reset the list of channels that are
available to the HP E1432A library.
As is always the case with interrupt handlers, it is easy to introduce bugs
into your program, and generally hard to track down these bugs. Be careful
when writing this function.
Data Gating
Sometimes you may wish to monitor data from some input channels and not
others. The function e1432_set_enable enables or disables data from an
input channel (or group of channels). If data is enabled, then the data can
be read using e1432_block_available and e1432_read_xxx_data. If data is
disabled, data from the specified channel is not made available to the host
computer.
This parameter can be changed while a measurement is running, to allow
the host computer to look at only some of the data being collected by the
HP E1432A module. While data from a channel is disabled the input
module continues to collect data but it is not made available to the host
computer. The host can then switch from looking at some channels to
looking at others during the measurement. In contrast, the function
e1432_set_active completely enables or disables a channel and can’t be
changed while a measurement is running.
For order tracking measurements this function can be used to switch
between receiving order tracking data, ordinary time data, or both.
HP E1432A User's Guide
The C-Language Host Interface Library
4-28
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