Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Thu, 17 Mar 2011 17:50:11 -0500

Release 2-2 of the EPICS "modbus" module is now available.  This is from
the release notes:

- R2-0 introduced a 20 ms delay before each Modbus write. This was not
correct, delays should only be needed for serial RTU. The Modicon Modbus
Protocol Reference Guide says this must be at least 3.5 character times,
e.g. about 3.5ms at 9600 baud, for Serial RTU. An additional
writeDelayMsec parameter was added to modbusInterposeConfig. It is the
final parameter, so if it is not specified the default value is zero,
which is appropriate when not using Serial RTU. In the startup script
lines like the following: 
    modbusInterposeConfig("Koyo1",0,5000)

should be changed to: 
    modbusInterposeConfig("Koyo1",0,5000,0)

for no delay, or to: 
    modbusInterposeConfig("Koyo1",0,5000,20)

for a 20 ms delay. 

The release notes are here:
http://cars.uchicago.edu/software/epics/modbusReleaseNotes.html

The documentation is here:
http://cars.uchicago.edu/software/epics/modbusDoc.html

The tar file is here:
http://cars.uchicago.edu/software/pub/modbusR2-2.tgz

Please let me know of any problems or questions.

Cheers,
Mark

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System