Can't get MITS Programming Package II Working [SOLVED]

General discussions related to the Altair 8800 Clone

Can't get MITS Programming Package II Working [SOLVED]

Postby RyanS » March 1st, 2015, 7:56 pm

I can't get MITS package II to respond to user input. I have loaded it (several times) from the cassette audio image, carefully following the instructions in the ReadMe PDF. I have also loaded it from the .TAP file using the 2SIO loader. I successfully get two spaces with a "?" prompt. It sure looks like it is working. However, no keyboard input of any kind gets echoed back. Nothing happens when I send a <CR>. (No new prompt shown, it looks like the <CR> is being ignored.) I have the terminal setup for 7 bits with space parity. The machine looks like it is in the right state. When I follow the instructions for restarting the monitor everything works as expected. I get a new " ?" prompt. However, all user input is ignored.

Can anyone recommend what I look at next? I am using the default TeraTerm settings from Mike. I am only adjusting the serial settings when I am supposed to be, according to the instructions.
Last edited by RyanS on March 3rd, 2015, 2:24 am, edited 1 time in total.
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Re: Can't get MITS Programming Package II Working

Postby Drunkle » March 1st, 2015, 11:02 pm

You may have done this already but if not, have a look on YouTube at Mike's video labeled:

Altair 8800 - Video #21 - MITS Programming System II (Introduction)

It details each step of the process well. It was what I used when I install the MITS Programming System II which did work for me.

It looks like you do have serial communications between your terminal and the Altair since you have used serial to send the .TAP. But just to be complete you might try the following:

AS a test start with making sure that hardware handshake is turned off. Normally this would no be an issue but just to make sure in Tera Term select Setup then Serial Port and set Flow control to none. Test your connection. If you still do not communications try the next test.

Lets try to isolate which side of the problem you are working. Serial port issues or Altair programming issues. One old school method I still use to debug serial lines is the simply unplugging the serial plug from the Altair and shorting pins 2 and 3 on the cable coming from your terminal (or PC with Tera Term). Lucky for us that there are male pins here which makes it easier to short them out. Once the pins are shorted, type characters on the terminal keyboard. If all is well you should get echoed back on the display everything you type. Pins 2 and 3 are the transmit and receive pins so you are just looping everything you send right back to your terminal. If this test fails (no characters echoed back) you are working some form of serial problem on the terminal side. Setting, bad cabling, etc.

If these tests work and the video does not show you something missed, the most likely issue is on the Altair side and I'll then defer to Mike's (or other's ideas).

Good luck with your goal and please let us know what you learned.
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Re: Can't get MITS Programming Package II Working

Postby AltairClone » March 2nd, 2015, 12:03 am

When loading the monitor, do you have A9 up or down? The simplest thing is to run with A9 UP which does serial input WITHOUT using interrupts.

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Re: Can't get MITS Programming Package II Working

Postby RyanS » March 2nd, 2015, 2:06 am

Thank you for the quick replies. Here is my follow up:

* My serial connection is working fine. Have used it extensively with all versions of BASIC and CPM.
* In order to ensure the USB to serial adapter wasn't messing with things, I switched to an older IBM laptop with a direct serial connection. Re-tested and got the same problem. I see the prompt, but no user input.

Now to the interesting stuff...
* When I raise A9 I am able to get echo! However....
* With A15, A11, A10 and A9 raised I got garbled input/output. But at least it was working.
* After fiddling with the settings I discovered I needed to use 7-S-2. Everything worked perfectly. 7-S-1 was giving garbled output. (With A11 and A10 up?)
* After I confirmed the monitor was working correctly in this state (ensuring the whole system was good). I re-loaded with A9 down (7-S-2). No dice. User input ignored.

So... Issue with two distinct setups? Did I tweak something in the config manager by accident? Bug in the loader? Bug in the emulation code some place? With A10 up I should have needed one stop bit, not two (according to the manual). I also don't understand why it won't work at all with A9 down. I suspect I'm right on top of the answer, if I knew anything about how serial communication works.

I have attached an image of the output. The first part shows output with A15, A11, A10 and A9 raised with 7-S-1 as I fiddle with the settings. Then you can see good output when I switched to 7-S-2. The very last line shows my final test with A9 down. It didn't work with 7-S-1 or 7-S-2... but I still get a prompt. *shrug*
Attachments
20150301-serial.jpg
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Re: Can't get MITS Programming Package II Working

Postby AltairClone » March 2nd, 2015, 7:38 pm

The setting of "7S1" in TeraTerm effectively makes TeraTerm ignore the parity bit since TeraTerm still displays characters received with a parity error. This is a common trick when using TeraTerm and is required for running 4K and 8K BASIC which use the MSbit of some characters as a flag. In the days of the Teletype, the value of the MSbit didn't make any difference since the Teletype ignored it.

HyperTerm, which I see you're using, is a different story. HyperTerm ignores characters with parity errors. Though not clearly documented, the MITS Programming System II (PS2) transmits characters as 7E1 (i.e., even parity). When you choose "7S1" on HyperTerm, it is ignoring any characters that don't have space parity. That's why the carriage return (parity bit is set from PS2) is ignored by HyperTerm. The line feed is accepted and moves down a line. I can't duplicate what you're seeing with "7S2" working. Did you maybe choose "7E2" by mistake? That would work.

If you're going to use HyperTerm, I'd use 7E1 or 7E2. Note that PS2 ignores received parity, that's why the general solution of 7S1 in TeraTerm works for most any Altair software configuration.

Regarding running with A9 down (interrupts enabled), you have to disable interrupts from the Real Time Clock on the 88-VI/RTC board and set the console 2SIO port to be on interrupt level 7. These options are in the "Interrupt Vector Assignments" menu of the Admin menu in the Clone. This is mentioned in the first part of the PS2 readme file.

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Re: Can't get MITS Programming Package II Working

Postby RyanS » March 3rd, 2015, 2:21 am

That did the trick. Thank you very much for the advice, Mike. I followed your instructions and was able to get it to work perfectly. Very interesting note regarding HyperTerm vs. TeraTerm. On the old laptop I only had HT available. I figured one emulator was as good as any other. You've certainly enlightened me. It is possible I didn't correctly write down the settings I was using with HT. It may have been 7E2.
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