Re: Plus/4 RS232 woes

From: smf <smf_at_null.net>
Date: Mon, 3 Sep 2018 18:03:53 +0100
Message-ID: <f76d3155-a6fa-b01b-cafa-1b343a35df47@null.net>
On 03/09/2018 17:26, Mike Stein wrote:
> Why would you 'change your mind' to say you're not Ready To Send while you're actually sending a character, without waiting for the character to be completely sent?

In full duplex RTS means I am ready to receive, nothing to do with 
sending (despite the name). So normally you start out with it low, then 
when you receive a character and your buffer is getting full, you raise 
RTS to tell the other end to stop sending (most UARTS at least have the 
flow control seemingly the wrong way round). If the 6551 disables the 
transmitter immediately, then you obviously have to wait until the next 
character time before you drop RTS.

In half duplex you only raise RTS when you have data to send and wait 
for CTS to be given in response. It seems 6551 is designed for this 
scenario, rather than full duplex flow control.
Received on 2018-09-03 20:00:04

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