Re: Developing PLATOTerm64, Flow Control woes.

From: smf <smf_at_null.net>
Date: Mon, 2 Jul 2018 09:10:11 +0100
Message-ID: <ac9ba5f1-9b21-20b7-cd9f-57b74710aadb@null.net>
On 01/07/2018 20:22, Mike Stein wrote:
> Keep in mind that XON/XOFF expects a fairly immediate response; a common issue using it these days is that you're not necessarily receiving single characters but packets and you could receive quite a few characters before XOFF has any effect.

The problem is large transmit fifo's and the uart neither understands 
the concept of flow control, nor allows the driver to pause 
transmission. If you also have a large dumb transmit fifo, then it may 
be a while before you can tell the other end to stop sending (and if the 
other end has sent an xoff then someone is going to be losing data). 
This affects you whether you're using packets or an ascii terminal.

xon/xoff also shouldn't be used as an end to end flow control over a 
modem/the internet as the transmit fifos in those will certainly swamp you.

sending xoff as soon as you start receiving and only sending xon once 
all the data has been processed is as extreme as you can get, if that 
doesn't work then the problem you're trying to solve is actually elsewhere.
Received on 2018-07-02 11:00:04

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