SYM-1 Hex Display Question

[mipspro]

I have recently resurrected a Synertek SYM-1 from some mishap in the past that killed most of it's major ICs and half it's LED display. I replaced the damaged components and everything seems to work now including RS-232 however I've noticed that when I hit any key on the hex keypad the display cuts out until I release it. This has the effect of flashing the displays every time I enter anything on the hex keypad. Normally it wouldn't have crossed my mind however my MicroKIM doesn't do this and neither do any KIM-1s I've seen. Since I can't find any YouTube videos of the hex keyboard in action I'm left wondering if this a normal behavior of the SYM-1/Supermon or do I have a short or still unknown damage in the display circuit?

[GARTHWILSON]

I'm not familiar with it, but it sounds like the keypad routine stays in a loop, depriving the display of strobing until you release a key. I really don't think there's anything wrong with the display.

[mikeblas]

Garth has it right; the monitor ROM polls for the key release while the key is down, so it's not refreshing the LEDs at that time. It's normal.

As you write code, you'll also have to keep in mind that a busy loop might want to call the monitor's scanning function every once in a while -- or setup an interrupt to do so, or ...

[mipspro]

I think you guys are right, it seems the GETKEY routine for the KIM-1 also scans the display while polling the keyboard, I'm guessing the SYM-1's Supermon does not so that's why the display does not update... I've found an article from MICRO that discusses adapting the KIM-1 routines for the SYM-1 to be able to run the games in "The First Book of KIM" so I'll currently working on that.

Thanks for the help!

[BillO]

I've never noticed this behavior on my SYM-1. I guess I could dig it out and check. I'm very much a hunt 'n' peck typist on that keypad, so it may just be that I did not notice it happening.

[mipspro]

It has to be an issue with the Supermon hex keyboard routines, I used the converted KIM-1 routines SCAND, SCANDS, GETKEY, etc. from the July 1979 issue of MICRO to run the basic "read keyboard, write to display" test program from the beginning of "The First Book of KIM". The program works, but the screen still does not refresh while the key is depressed as it does on the KIM-1/MicroKIM. This probably has to do with the converted routines basically being wrappers around their SYM counterparts. Unfortunately this would make some games really annoying to play.

SYM-1:
https://www.youtube.com/watch?v=I8OvN1Cd2fk

MicroKIM:
https://www.youtube.com/watch?v=LEUnQJUzZz4

Does anyone have a copy of "The SYM/KIM appendix to the First book of KIM" by Robert A. Peck? It would be nice to take a look at but it seems to be lost to history...

[okwatts]

I have a copy of Peck's leaflet/book I'll try and scan it. When I get that done I'll let you know.

[okwatts]

Okay I have scanned the book and finally got the pages in the correct order. I have emailed Mike about uploading for inclusion in the Sym-1 resources section. I'm waiting for a reply as to whether it's permitted to share the content.

[mipspro]

WOW! That's awesome news!

[mipspro]

I was able to get the PDF of "The SYM/KIM Appendix to the First Book of KIM" from okwatts (Thank you!) and here at long last is "Asteroid" running on a SYM-1:

https://www.youtube.com/watch?v=d1a-FScq2Eo

It plays pretty much like the KIM-1 version, except that the screen kinda glitches when the keys are pressed, this doesn't happen on the KIM-1 and I believe this is normal and from the way the 74145 is interfaced to the 7-segment displays/keyboard on the SYM-1 as they added a speaker and the decimal point... I guess since they gave you the option of 3 6522s they figured you can just wire up your own joystick

I hope the PDF is added to the Synertek section of 6502.org, if this site and it's info didn't exist my formerly fried SYM-1 would probably have stayed in it's box forever...