ASCI u68 (SystemX)

Henk Gooijen henk.gooijen at
Sat Oct 17 03:10:03 CDT 2015

OK. Did you post a link to some pictures? That can be helpful,
I missed the link if you did post it. The picture can help in
understanding what you have. I already know it has the 6800 :-)
and three 6821 PIAs. Is there also a 6850 ACIA on board?
Do you have some documentation?  It could well be possible that
all you have after power up is the keypad and 7-segment displays
as on the MEK6800D2.
Check the power supply on the M6800 CPU. If you have a scope
you can check for activiy on the address and data pins, and the
"phi2" pin and VMA pin. I f we get further I probably need to get
the M6800 user manual on my desk.

- Henk

-----Oorspronkelijk bericht----- 
From: Brad
Sent: Friday, October 16, 2015 10:37 PM
To: 'General Discussion: On-Topic and Off-Topic Posts'
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 
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 Posts'
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 

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 opcodes!
INX=$08, LDA # =$86, DEX=$09, STAindexed =$A6. etc.
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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