#: 21253 S12/OS9/68000 (OSK)
    31-Oct-95  05:35:40
Sb: #21252-#SCF hardware handshake
Fm: Marc Tritschler 100344,2706
To: Doug Bailey 73612,2146 (X)

The ability of your system to work with CTS/RTS flow control depends on two
things - the ability of your actual serial communications device to handle flow
control, and the device driver itself having the ability to configure the
device to do so.

It is safe to assume that your serial device has the ability to handle flow
control, but the device driver is another question. The device driver will
have, most likely, been supplied to you by the company you have bought your
hardware from, and so I would recommend that you speak to them to get an
accurate answer.

I will give you an example of my SCF device driver experiences. In the SCF
device drivers that I have, CTS / RTS flow control is enabled by using the
xmode utility to set the XON and XOFF properties to certain values not normally
used for XON and XOFF e.g. both to 0. The device driver, when it picks this up,
puts the device into CTS / RTS flow control mode.
Unfortunately, however, the manufacturers definition of flow control was not
the same as mine - they asserted RTS permanently (whether or not data was ready
to be transmitted) and waited for CTS to be asserted before transmitting data,
whereas I required to assert RTS only when I had data available to send, and
wait for CTS to be asserted before sending it, then de-assert RTS after the
data was sent. In order to achieve this I had to modify the device driver
itself, which required fairly in-depth knowledge about the device.

Obviously, if you dont have this knowledge, and need to do a similar
modification, it is better to get the manufacturer / device driver supplier to
do it for you.

I hope this puts things into perspective.

Cheers,

Marc.

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