Altair UIO Interrupts

Discuss construction, troubleshooting, and operation of the Altair 8800c computer

Altair UIO Interrupts

Postby toml_12953 » April 8th, 2019, 4:09 am

To set the ACR board interrupt, you connect one of three pads to one of the eight interrupt priority level pads (0-7)
These pads are labeled OUT, IN and BH (for BotH)

The UIO also has three pads labeled RINT, WINT and SI. I figure RINT is Read INTerrupt (like IN) and WINT is Write INTerrupt (like OUT)
but I can't figure SI. Is that analogous to BH somehow?

If it is, I only need one wire connecting SI to the level I choose.
If not, then I need two: RINT to level and WINT to level.
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Re: Altair UIO Interrupts

Postby AltairClone » April 8th, 2019, 11:56 am

Other than Timesharing BASIC, no Altair software uses interrupts, so in general, I would not jumper anything to interrupts 0-7 or PINT.

If you want to use the serial I/O port as another terminal for Timesharing BASIC, then strap the SI pad to the desired interrupt level 0-7. SI stands for "S"erial "I"nterrupt and comes from the 6850 UART used for terminal I/O. You'll need to make sure your 2SIO ports and the serial port on the UIO are all at different I/O addresses.

RINT and WINT are the read interrupt and write interrupt lines for ACR I/O, but again, no Altair software uses interrupts for cassette I/O so I would not connect them.

I do not see the OUT, IN, and BH pads you reference on my board. Where are they located?

Mike
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Re: Altair UIO Interrupts

Postby toml_12953 » April 8th, 2019, 12:59 pm

AltairClone wrote:Other than Timesharing BASIC, no Altair software uses interrupts, so in general, I would not jumper anything to interrupts 0-7 or PINT.

If you want to use the serial I/O port as another terminal for Timesharing BASIC, then strap the SI pad to the desired interrupt level 0-7. SI stands for "S"erial "I"nterrupt and comes from the 6850 UART used for terminal I/O. You'll need to make sure your 2SIO ports and the serial port on the UIO are all at different I/O addresses.

RINT and WINT are the read interrupt and write interrupt lines for ACR I/O, but again, no Altair software uses interrupts for cassette I/O so I would not connect them.

I do not see the OUT, IN, and BH pads you reference on my board. Where are they located?

Mike


They're on the ACR board, not the UIO board. Quote from page 23 of the ACR manual (I don't have an ACR)

"There are three pads at the top of the board labeled "OUT", "IN" and "BH". There are eight pads at the bottom of the board numbered 0 through 7. The eight numbered pads correspond to the eight priority levels respectively. "

"You may connect the "OUT" (output device) pad to some priority level, and the "IN" (input device) pad to some priority level; or you may connect the "BH" (both devices) pad to a desired priority level for both devices. If the "BH" pad is used to set the priority level, the "OUT" and "IN" pads should not be used."
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Re: Altair UIO Interrupts

Postby toml_12953 » April 8th, 2019, 9:46 pm

AltairClone wrote:SI stands for "S"erial "I"nterrupt and comes from the 6850 UART used for terminal I/O. Mike


I looked in the "Using the UIO Board" manual I have (17 pages) and it doesn't mention SI anywhere. Do you have a more complete manual?
If so is it available online somewhere? If not could I get a copy?

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Re: Altair UIO Interrupts

Postby AltairClone » April 8th, 2019, 10:18 pm

I don’t know of any other UIO documentation. I’ve been looking at the schematics to obtain additional information.

I pulled out my UIO tonite and did some preliminary testing. The power supplies look good, the tantalum capacitors didn’t blow, and the console port works. I haven’t done any cassette testing yet.

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Re: Altair UIO Interrupts

Postby virtualaltair » April 11th, 2019, 10:46 pm

> Other than Timesharing BASIC, no Altair software uses interrupts, so in general, I would not jumper anything to interrupts 0-7 or PINT.

Does a system with interrupt jumpers connected on daughter boards have problems running single-user MITS BASIC, MITS DOS, or CP/M?

Can Timesharing BASIC run single-user without interrupt jumpers?
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Re: Altair UIO Interrupts

Postby toml_12953 » April 12th, 2019, 1:14 am

virtualaltair wrote:> Other than Timesharing BASIC, no Altair software uses interrupts, so in general, I would not jumper anything to interrupts 0-7 or PINT.

Does a system with interrupt jumpers connected on daughter boards have problems running single-user MITS BASIC, MITS DOS, or CP/M?

Can Timesharing BASIC run single-user without interrupt jumpers?


1. Single user BASIC, CP/M, etc. ignore the interrupt vectors since they don't generate interrupts. They work fine with the VI/RTC board installed and interrupts enabled on the boards.

2. No, TS BASIC always generates interrupts even with only one terminal so you need a VI board and each board you want to use has to be strapped to an interrupt vector. Boards that don't have one won't be recognized by TS BASIC.

A bare repro VI/RTC board is readily available and easy to build (Even I did it successfully!) I'd recommend it even if only for the real-time clock!

Here's one source for the VI/RTC board:

http://jmprecision.co.uk/shopping/pgm-more_information.php?id=134&=SID#MOREINFO

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