My KIM-1 won't add two numbers.

[RonH]

Hi Everyone,

I am new here.
My KIM-1 (Rev G) sat for about 45 years

Yesterday, it powered up fine.
I entered the program from the User Manual that adds 2 numbers.
I confirmed the program in memory.

But when I press GO, the display just goes black; the sum is not displayed.
I'm not sure about the correct position of the SST slide switch (my keyboard has that switch on the left).
But I do think I tried both positions with the same result.
(I'm going to double check this.)

My scope shows a good 1 MHz square wave between E-Y and E-22.
I don't know what else to check because I don't know much about how the board works.
I'll be reading the manuals.

Any suggestions, welcome!
RonH

[barrym95838]

Welcome, RonH!

I'm not a KIM-1 expert, but one should be here shortly. I believe that the display is continuously refreshed by the firmware, so if you crashed it with an improper exit you might have really added the numbers but are just unable to view the result.

[BigEd]

Welcome! This looks like the relevant part of the manual:
https://www.kim-1.com/usrman.htm#24

Was it the case that the display showed 0002 just before you pressed GO?

[BigEd]

Ah, we can follow the same process at
https://maksimkorzh.github.io/KIM-1/
the KIM-1 on the web.

[BigEd]

As Mike says, the most important part is the final jump back into the monitor.

You should I think have entered something like this:

Code: Select all

Address  Hexdump   Dissassembly
-------------------------------
$0002    18        CLC 
$0003    A5 00     LDA $00
$0005    65 01     ADC $01
$0007    85 FA     STA $FA
$0009    A9 00     LDA #$00
$000B    85 FB     STA $FB
$000D    4C 4F 1C  JMP $1C4F

So the bytes at 000D onwards should be 4C 4F 1C. But you say you did verify the memory content.

Edit: that listing/disassembly is the result of assembling this program:

Code: Select all

define	VAL1	  $00
define	VAL2	  $01
define	POINTL	$fa
define	POINTH	$fb
define	START	 $1c4f

PROG:	CLC
		  LDA VAL1
        ADC VAL2
        STA POINTL
        LDA #00
        STA POINTH
        JMP START

[RonH]

It's ALIVE!
I'm not sure what the issue was.
When I went back and double checked, it worked on the first try.
I confirmed I knew what I was doing by changing the 2 numbers and correctly predicting the sum.

And wow! This is a great place!
Thank you guys for the quick replies.
Yes that's the program.
The simulator is great.

Next (tomorrow?) I will fix my wiring for the cassette interface and see if I can find a recorder.
I think I remember from back in the day a warning not to use one with automatic recording level control.
I also think I remember playing with the pot you are not supposed to touch.
So, this may take a bit of work.

Thanks again!

[BigEd]

Great news!

[6502inside]

Could be flaky RAM. KIMs are notorious for that. My original suitcase KIM-1 would have weird intermittent lockups when it heated up until the bad RAM chip failed completely, and had to be replaced. After that it's worked like a champ. If you can find one of Dwight Elvey's debug boards, those will help a *lot*.

[BigEd]

Here's Hans Otten's page describing that board (links within!)
KIM-1 Diagnostic Board

[HansO]

First things to do on a KIM-1 (see the sticker attached from my original KIM-1)

Fill in the vectors, so Break /Stop/NMI works works.

Clear decimal 00F1 to 00 at least

Then press Go.