ASCI u68 (SystemX)

Mike Stein mhs.stein at
Fri Oct 16 15:55:29 CDT 2015

Often you have to press RETURN or SPACE a few 
times to wake up the serial connection and set the 
baud rate; if you put a scope on the RX and TX 
lines, do you see the incoming signal from the 
terminal and does anything get sent back?

Can you trace the RX and TX signals to see what 
chips are used to convert RS-232 to TTL?


----- Original Message ----- 
From: "Brad" <unclefalter at>
To: "'General Discussion: On-Topic and Off-Topic 
Posts'" <cctalk at>
Sent: Friday, October 16, 2015 4:37 PM
Subject: RE: ASCI u68 (SystemX)

Thanks Henk,

I tried that.  No prompt comes up with PUTTY on 
serial set at any baud rate.    Instead on the LED 
display I get a C, or an S sometimes.

-----Original Message-----
From: cctalk 
[mailto:cctalk-bounces at] On Behalf 
Of Henk Gooijen
Sent: Friday, October 16, 2015 11:56 AM
To: General Discussion: On-Topic and Off-Topic 
Posts <cctalk at>
Subject: Re: ASCI u68 (SystemX)

-----Oorspronkelijk bericht-----
From: Brad
Sent: Friday, October 16, 2015 8:27 PM
To: 'General Discussion: On-Topic and Off-Topic 
Subject: RE: ASCI u68 (SystemX)

Many thanks.  I'll take a quick look online just 
to see if I can save you the trouble.  I'm 
surprised at how little documentation there is for 
this thing.

As a general rule, does anyone know -- if you have 
a single board computer like this with serial 
connector, is that 'live' all the time?  Or do you 
usually have to invoke a program in order for a 
terminal to connect to it and use it?

>From all the SBCs that I know, the standard serial 
port is always active. The on-board monitor with 
very basic commands uses it as only means of 
After reset the monitor will "print" possible a 
one-line identification and on the next line some 
form of prompt.
Could be * or .  or > or - or whatever.

You need to know the com ports settings, but it 
prints an ID line you can try several baudrates. 
9600 is a good start.

If you want 6800 info, ask. I can dream 6800 
INX=$08, LDA # =$86, DEX=$09, STAindexed =$A6. 
Depending on the RAM size, I have a StarTrek 
version in 6800 assembler that uses a serial port 
... IIRC, it is some 1.5k

- Henk

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