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Bringing up my Altair system serial I/O National Multiplex 2SIO questions

17again

Member
Joined
Sep 23, 2019
Messages
22
Location
United States, Dallas Texas
Hey All,

Taking my time bringing up my Altair system. It has a REV 0 8080 CPU board, I had to replace a cap on the 32K RAM card and now I can examine memory and deposit into zero page RAM. I have a National Multiplex 2SIO card and I've checked the manual and the 2nd serial port is wired for RS232. I've verified the transmit, receive, ground RTS-CTS DTR-DSR are connected correctly. I'm trying to understand this card more and I see there is a built in monitor, but how do I configure baud, stop bits etc? Also, the manual says C000 but the ROM is labeled F000 and data is in F000 not C000. I just want to examine some memory at this point, I'm ready to connect but a little stumped at the baud rate settings.
 

alan8086

Experienced Member
Joined
Oct 1, 2016
Messages
325
Location
Burnley, UK
Hi, I have no useful suggestions - just know that I too have an S100 system (but not a lot of knowledge) and am here awaiting further replies to your question - more for edutainment purposes:)
 

alan8086

Experienced Member
Joined
Oct 1, 2016
Messages
325
Location
Burnley, UK
Cant you just connect via null modem cable to a PC with Hyperterminal ( or modern equivalent ) and try different settings? My S100 box worked off defaults after setting to 9600baud inWindows device manager - or is the issue that you have no boot ROM and its all entering boot code via front panel etc? I'm probably just embarrassing myself here - I'm sure someone will come along soon....
 

17again

Member
Joined
Sep 23, 2019
Messages
22
Location
United States, Dallas Texas
I found the jumper settings for 8 bit, 1-N so now just playing a guessing game at the baud rate I guess lol. And a guess for the F000 address code is a monitor program. I'm connecting to an old P4 laptop with a serial port using a null modem cable.
 

gamer-stu

New Member
Joined
Apr 14, 2008
Messages
4
You might find it helpful to use an rs232 breakout box to help with debugging. The one I have has LEDs for each line, and allows for patching in different combinations.
 
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