Date   : Wed, 18 Jul 2012 22:24:00 +0200
From   : vanekp@... (P. Van Ek)
Subject: RS423 won't transmit. Dead 6850?

Normally with serial ports its the TX/RX chips that go, which in the case of 
the BBC micro are IC74(RX) (DS88LS120N) IC75(TX) (DS3691N)
In your case you say it can receive then it could be IC75-DS3691N that is 
faulty.

Regards Peter.

----- Original Message ----- 
From: "Matthew Walker" <walker_matt@...>
To: <bbc-micro@...>
Sent: Wednesday, July 18, 2012 22:10
Subject: [BBC-Micro] RS423 won't transmit. Dead 6850?


> I've a plain Issue 7, which can't transmit anything from the RS423 port.
> It can receive fine (just *fx7,6 *fx 2,1 then type stuff on a PC)
> Sending however, nothing. I tried sending stuff with *fx5,2 then *fx8,6
> but nothing appeared at the PC end. I know it's not the cable at fault
> so I tried swapping the serial ULA, which made no difference. I had a
> look at pin 6 of IC4 the 6850 ACIA, which is permanently high regardless
> of weather the ULA was in place or not. I'm assuming that the 6850 is
> dead, but seeing as it's soldered in and will be a pain to remove, does
> anyone have any ideas I could try before I have to de-solder the 6850?
>
>
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