Experimental Physics and Industrial Control System
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On Jun 29, 2009, at 11:27 PM, Patrick Thomas wrote:
Hi,
Two questions:
1) Does the asyn record block when reading until the requested
amount of bytes (NRRD) is available in the serial fifo buffer, or
does it only block until 1 byte is available (like the c read
function), or not at all?
The asyn record performas a single asynOctet read operation. The
semantics of this depend on the underlying asynOctet driver and any
interposed layers. The low-level serial driver, for example, behaves
like the POSIX read() routine -- a read request returns as much data
is available, up to the size of the request. The asynInterposeEos
layer can be stacked on top of the low-level serial driver and will
loop until the specified 'end-of-string' sequence has been read (or
the read count has been satisfied, or some other 'end-of-message'
condition has been met).
2) Is there a way to check that it has gotten all the requested
bytes into the record before doing a caget on the BINP field to
retrieve them?
The EOMR 'End Of Message Reason' field contains bits describing the
conditions that terminated the read. The ASYN_EOM_CNT bit is set when
the full number of requested characters have been read.
Thank you for your time,
Patrick
--
Eric Norum <[email protected]>
Advanced Photon Source
Argonne National Laboratory
(630) 252-4793
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ANJ, 31 Jan 2014 |
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