PSI BOX PLUS+ Reference
Control Functions
NO TO.
Disable The Timeouts.
_______
____________________
Purpose.
To make the PSI BOX wait indefinitely in a bus
__________
handshake routine till the responding device is ready for the data
transfer.
When the PSI BOX is exchanging data with a bus device
it may need to wait a long time for the data to become present,
or for the device to make data available. The NO TO command
can be used to make the PSI BOX wait indefinitely for the
device to be ready to handshake data. By contrast the TO
command can be used to set the maximum time that the PSI
BOX waits for the device to become ready.
Whilst most IEEE devices are fast enough to quickly
respond to your PSI BOX, IEEE printers and most especially
IEEE plotters are quite slow devices. When the printer or plotter
buffer fills up the PSI BOX must wait for it to print the current
buffer contents and so make room for more input. During this
wait time the PSI BOX will timeout the IEEE printer or plotter.
To prevent this timeout occuring and so causing the program to
think that the printer has gone dead, you should specify the NO
TO, no timeout, option.
Now the PSI BOX will always wait until the plotter or printer
can cope with the data it receives.
Two Notes Of Caution!.
a) If the printer or plotter hangs up due to some reason or other
the PSI BOX will not timeout but will continue to wait.
b) Be sure that you have properly set the EOS byte for
terminating inputs. If the PSI BOX does not know how to
recognise the last byte in the input sequence it may go on to ask
for more and so wait indefinitely if the Talker has no more to
send. See the EOS command.
Bytes 57 and 58 in the IEEE control status string contains
the current timeout value. A value of 0 indicates that the
timeouts have been disabled.
The timeouts step up in 1,2,5,10 increments from 1
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Chapter 8
