OK past the 3p+s Hanging issue, now the next problem...

[Corey986]

The previous problem was an issue with my -12v supply on the rev 0 motherboard and the tantalum caps all needing replacing.... with that done, the machine resets fine...

So...

I've jumpered the card to emulate a MITS SIO2 port 0 @20/21

I tried the "echo" program from the basic manual/solvient website. No go... No echo...

So I think I still have to sort out the card since it was an ebay special and I have no clue if it works in the first place.

First step before I start major debug was to try the following (I hope my
assumptions here are right, let me know if its not).... When I got the card the
mc1489 chip was missing so maybe there is something up there, sometimes you need
to be a detective.

I checked my terminal emulation program by tying both serial in/out with a
paperclip and the echo works.

Next I hooked up on the 3P+S card's MC1489 and MC1488 terminal 4 to each other.
Then I
hooked up the edge connector J2 pin 12 to RS-232 signal ground, J2 pin N and
J1 pin R to the appropriate RS232 connectors. I even tried it with and without
a null modem in case I was an idiot and wired it backwards....

Turned on the altair so that the card had power and tried my terminal program...
no echo...

I would think this should work, correct? The RS232 level should be available on
the MC1489 and MC1488 as TTL level at terminal 4 for each and tying them
together should be a simple way to test an echo.

Or am I wrong....

If this is the case that is should work, I will borrow some spares of both chips and test.

If my test shouldn't work, then any advice on where to start. I have already
dragged my scope upstairs and should hopefully be getting an extender card early
this week.

 

[Marty]

Hi Corey;
Not knowing what pin 4 is, I can't say that you are or are not doing the correct thing... What I would do is a couple of things.. one, is trace back from the appropiate pins on your RS-232. If you have a DB-25 then its pins 2 and 3 for the signals and 7 for Ground.. I don't know what it is for a DB-9.. Trace pin 2 from your cable to the Card, and make sure you have (with an ohm meter) the signal going all the way to the IC.. do the same for pin 3.. look up how the 1488 or 1489 are wired up, then (If your 1488 and 1489 are socketed, take them out and wire the appropriate pins together and make sure you can get an echo, on the terminal side.. do the same thing for the Altair side, trace back from the Ic's to the input or output to or from the 1488 or 1489.. Write a half echo program, one that when you have loaded the A Accumulator with say a letter, then send it out to port 20/21, (remember that port 20 is status and that 21 is data) you should get it displayed on the screen.. After doing that get it to accept an input from the terminal and display it on the Altairs lights.. After having both working seperately, you should be able to get the echo program to work.. Read over the other postings on the SSM I/O and the Altair 2-SIO..
THANK YOU marty

 

[Marty]

Hi Corey;
I just looked at my PT manual.. and pin 2 on the DB-25 goes to J1-R and pin 3 goes to J2-K.. so with 1488 and 1489 pulled connect together pin 8 on the 1488 and pin 1 on the 1489 and your terminal should be able to echo.. next put in both chips and short pins 9 or 10 on the 1488 to pin 3 on the 1489, and you still should get it to echo.. If not you have either a bad IC or both are bad.. Then you can try the half echo I suggested earlier.. I am assuming that my manual is for your board, but it may not be so, and then use an ohm meter to find the correct pins..
THANK YOU Marty

 

[Corey986]

Well past that now...

I had a bad connection on my test wires for the jumper. But card still isn't up...

As per some help on the Altair yahoo forum, I have verified that pin 19 on the UART is going high when I send a character so something is working. Just not all of it.

I should be able to do a better triage later in the week with the addition of a bus extender.

Thanks,
Corey

 

[Marty]

Hi Corey;
I would still suggest, that you .. do a half echo to find out which side is not working.. sending a fixed character to the terminal.. and pressing a key and have it show up on the Altair front Panel..
THANK YOU Marty