SunOS real time problems

[EAJUAN at TOP.UPC.ES]

At our Institute we have lots of headaches trying to tackle real time
applications with a SUN 4/260 (SunOS 4.0.1, 32 Mb main memory) and I would
greatly appreciate that somebody gave me a clue about how to solve them.

Our main problem is the following one : we have a PUMA 560 robot (with a
MK-II controller) connected through a serial line to the Sun workstation.
To maintain the dialogue with the robot we must make sure that the host
will answer the messages sent by the robot controller (each 28 ms.) before
receiving the following message (that is, within the next 28 ms.).  We
have tried working with the Sun as single user, raising the priority of
the process, etc... but it seems that there is no way of making sure that
the workstation will answer the message of the controller within the
alloted time. In fact, the program maintains the dialogue during a
variable number of intervals. Then, it fails to answer within the 28 ms.
period and the communication is broken.

Has anybody some idea about how to guarantee an answer of the workstation
within a given time period ?

Thanks in advance and best regards from Spain.

           Joan Ilari i Valenti     EAJUAN%EBRUPC51.BITNET at CUNYVM.CUNY.EDU
           Assoc. Professor         EAJUAN%TOP.UPC.ES at CUNYVM.CUNY.EDU