RE: mbbo/mbbi and bits subset

[<peter.owens@stfc.ac.uk>]

You can use the NOBT and SHFT fields to specifiy a subset of bits.
This is straightforward for input - simply read the whole register into an mbbiDirect record then have mbbi records use that record as their input using NOBT and SHFT to specify which bits to mask off.

For output it is more complicated. The whole word will be written to the record however you specify the subset of bits you are interested in. Do you want the other bits to be all zeros, or whatever you last wrote, or does it not matter?

Pete


-----Original Message-----
From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of gennaro.tortone@na.infn.it
Sent: 10 March 2016 10:54
To: tech-talk@aps.anl.gov
Subject: mbbo/mbbi and bits subset


Hi,
I'm using mbbo and mbbi record types to write and read some registers from/to ASYN driver I'm developing;

some registers refers to a single aspect of acquisition (e.g. channel threshold) and with a simple mbbo record to write and a mbbi record to read back, everything works fine...

other registers refers to a setup/control functions and using the same mbbo/mbbi approach works fine if the user address (read/write) every time the whole register;

I know mbboDirect for bitwise access of a record value but is there a method to address (read/write) through a record a "bits subset" of a "main" mbbo record ?

e.g. acquisition control:

         bit[16...2]	<don't care>

 	bit[1...0]
 	  11		stop acquisition
 	  10		start acquisition
 	  01		do something...
 	  00 		do something...

which is a simple method to access "directly" bitset [0...1] in order to have a record I can use to write 11 (3) to stop acquisition,
10 (2) to start acquisiton and so on ?

Thanks in advance,
Gennaro

--
Gennaro Tortone
INFN Napoli
Italy
tel: +39 81 676169

"Computer Science is no more about computers
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