Help with simple echo test on 88-2SIOR1

[Joseph Corda]

Greetings
I am in the process of building up a "Altair like" system.  Once the system is built and working it will be placed into a real nice wooded case Walt Perko created for me. 

At this point I'm currently trying to just do basic testing with a new 88-2SIOR1 card I have.
My current setup:

• N8VEM 9 slot backplane
• SD SBC-200 (Z80): Single board computer. 1k Ram (F800), TMON monitor running from FC00 in EPROM using the built in serial port connected to a terminal. 
• 88-2SIOR1:  Built and tested by Patrick prior to shipping,  configured for I/O 10h/11h,  dip set to 9600 and using port 0 DCE cabled to another terminal. I have tried SW1 with all switches off and on to make sure CTS..etc are okay.  
• Both terminals are setup as 9600,N,8,1 and have been tested.  I confirmed SBC-200 builtin serial and parallel port I/O do not conflict with the 88-2SIOR1 (Serial 7C/7D Parallel 7E/7F).

To test I wrote a (2) simple 8080 Assembly programs for the 88-2SIOR1, 1 to print "Hello World" and another to echo keys pressed and then print "---"<cr><lf>.  These programs assembled and runs on the AltairZ80 simulator under CPM (using ORG 0100h)  (see source files attach). 

With TMON I can load the assembled HEX file into the SBC-200 built in RAM and dump to verify it is loaded properly.  Next with TMON I use 'k sf800' to call the program .  Here are the results:

• hw1.hex:  No output on 88-2SIO connected terminal and returns to TMON prompt
• hw2.hex:  No output on 88-2SIO connected terminal and since it's a infinite loop TMON never returns.  A reset is require to recover.

I am sure there is something I'm doing wrong but i just cant put my finger on the issue. Also note that since I have not built my front panel yet I do not have any way to single step the code.  Any suggestions or guidance would be appreciated. 
Thanks
Joe

[Patrick Linstruth]

Are you using the DTE or DCE connector on the 2SIOR1?

What does the cable look like between the 2SIOR1 and your computer?

Do you have SW1-1 and SW1-2 on or off?

Are both the TX and RX LEDs on?

Set your baud rate to 300. When you run your program, does the TX LED blink?:

HW2.ASM may not work without setting up the stack pointer where there is RAM.

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<hw1.asm><hw2.asm>

[Joseph Corda]

Patrick 
Thanks for the reply...   See my answers below.
Can I ask does it look like I resetting the 88-2SIO correctly :
MVI     A, 03H      ; Reset 2SIO port
OUT     10H         ; Output to control port

MVI     A, 15H      ; Set 2SIO port to 8N1 (8 data bits, no parity, 1 stop bit)

OUT     10H         ; Output to control port

Also my CPU is a Z80 but I realized I was coding in 8080 Assembler.. which I understand should work.  Could l that be a issue?
I have used similar 8080 code to test the serial port on the SD SBC -200(z80) when I first got it and it work well.

Thanks
Joe

On Tuesday, August 19, 2025 at 11:58:22 AM UTC-4  wrote:

Are you using the DTE or DCE connector on the 2SIOR1?

Using DCE 

 

What does the cable look like between the 2SIOR1 and your computer?

Using supplied 9 pin cable to 9 pin usb serial converter connected to laptop running Ubuntu 24.04 and minicom. 
I have tried it with and without my serial break out box (for leds to see whats happening) between the 9 pin connectors.
Also I have used a 9 to 25 pin converted and 25 straight cable to a vt520 terminal.

Both of these terminal setup work with the SDSBC-200 built in serial port.
  

 

 

Do you have SW1-1 and SW1-2 on or off?

I have tried both on and off ..current SW1/2 on .. 3/4 off

 

 

Are both the TX and RX LEDs on?

yes both on and red 

Set your baud rate to 300. When you run your program, does the TX LED blink?:

I will try 300 baud later tonight after work and let you know what I see

HW2.ASM may not work without setting up the stack pointer where there is RAM.

I am fairly new with 8080/z80 assembler .. so I will look into setting up a stack point to see if that helps

 

On Aug 19, 2025, at 9:58 AM, Joseph Corda wrote:

Greetings
I am in the process of building up a "Altair like" system.  Once the system is built and working it will be placed into a real nice wooded case Walt Perko created for me. 

At this point I'm currently trying to just do basic testing with a new 88-2SIOR1 card I have.
My current setup:

• N8VEM 9 slot backplane
• SD SBC-200 (Z80): Single board computer. 1k Ram (F800), TMON monitor running from FC00 in EPROM using the built in serial port connected to a terminal. 
• 88-2SIOR1:  Built and tested by Patrick prior to shipping,  configured for I/O 10h/11h,  dip set to 9600 and using port 0 DCE cabled to another terminal. I have tried SW1 with all switches off and on to make sure CTS..etc are okay.  
• Both terminals are setup as 9600,N,8,1 and have been tested.  I confirmed SBC-200 builtin serial and parallel port I/O do not conflict with the 88-2SIOR1 (Serial 7C/7D Parallel 7E/7F).

To test I wrote a (2) simple 8080 Assembly programs for the 88-2SIOR1, 1 to print "Hello World" and another to echo keys pressed and then print "---"<cr><lf>.  These programs assembled and runs on the AltairZ80 simulator under CPM (using ORG 0100h)  (see source files attach). 

With TMON I can load the assembled HEX file into the SBC-200 built in RAM and dump to verify it is loaded properly.  Next with TMON I use 'k sf800' to call the program .  Here are the results:

• hw1.hex:  No output on 88-2SIO connected terminal and returns to TMON prompt
• hw2.hex:  No output on 88-2SIO connected terminal and since it's a infinite loop TMON never returns.  A reset is require to recover.

I am sure there is something I'm doing wrong but i just cant put my finger on the issue. Also note that since I have not built my front panel yet I do not have any way to single step the code.  Any suggestions or guidance would be appreciated. 
Thanks
Joe

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[Patrick Linstruth]

The program looks good and it looks like you have everything set up correctly.

One of the 2SIO (6850) gotcha’s is it will not transmit unless CTS is present. SW1-1,2 ON makes the 6850 think there is DCD and CTS all the time, so that shouldn’t be an issue.

I am envious you have an SBC-200. I have just resurrected SDOS 1.8B and CP/M 2.2R4 for the SBC-200 and VersaFloppy II. I had to add those devices to the AltairZ80 simulator to get it all working. I have a VersaFloppy II but not the SBC-200.

I am very curious which ROMs you have on your SBC-200.

There has to be a reason your 2SIO isn’t sending data out the port. More thinking…

Walt and I have been thinking of starting Zoom meetings similar to the S100 Zoom meetings but more geared towards brining up vintage hardware (and replicas) and software, not new incompatible boards and FPGA stuff. Would you be interested in something like that?

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[Altair 8800]

Can you modify your program to store in a memory address what is returned from the status register after resetting the 6850, return to TMON and then dump the value? It would nice to know if what IN 10H is returning makes and sense.

[Joseph Corda]

Patrick
I'll be sure to keep SW1-2 on.... 

Walt also mentioned a possible Zoom call... Yeah  I would be interested in joining!

As for ROMS .. The SBC-200 didn't come with any ROMS .. so that's where I started with my TEST scripts and burning them to EPROM to test the serial port..  About the time I got serial echoing working.. I met a person online (I only know them as "CJS" located in Japan) who had a monitor program called TMON and they wanted to add SD SBC-200 support.  They worked with me and got TMON mostly working.  Honestly they have been a big help to me getting the SBC-200 functional.  

Joe

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[Joseph Corda]

Patrick
Before we get to far I tested the new card you sent and I have the same results:
        ports 10/11H do not work
        port 12/13H works fine
So thinking its got to be the SBC-200 ..
Sorry about all the trouble I put you thru ..I really appreciate your assistance..
Joe 

Per your request which I just saw today to dump status after rest .. here are the results
I adjusted my script to save status to ADDR F900 after reset then return to TMON ..below is the output

Brief summary
1) force F900-F907 to AA
2) loaded program testing 10/11H and started it (k)
3) dumped F900 shows FF
2) loaded program testing 12/13H and started it (k)
3) dumped F900 shows 00

On Friday, August 22, 2025 at 2:37:24 PM UTC-4 Altair 8800 wrote:

Can you modify your program to store in a memory address what is returned from the status register after resetting the 6850, return to TMON and then dump the value? It would nice to know if what IN 10H is returning makes and sense.

On Tuesday, August 19, 2025 at 2:43:18 PM UTC-4 Patrick Linstruth wrote:

The program looks good and it looks like you have everything set up correctly.

One of the 2SIO (6850) gotcha’s is it will not transmit unless CTS is present. SW1-1,2 ON makes the 6850 think there is DCD and CTS all the time, so that shouldn’t be an issue.

I am envious you have an SBC-200. I have just resurrected SDOS 1.8B and CP/M 2.2R4 for the SBC-200 and VersaFloppy II. I had to add those devices to the AltairZ80 simulator to get it all working. I have a VersaFloppy II but not the SBC-200.

I am very curious which ROMs you have on your SBC-200.

There has to be a reason your 2SIO isn’t sending data out the port. More thinking…

Walt and I have been thinking of starting Zoom meetings similar to the S100 Zoom meetings but more geared towards brining up vintage hardware (and replicas) and software, not new incompatible boards and FPGA stuff. Would you be interested in something like that?