How to write to digital I/O LEDs?

[liamoc]

Hi, thanks for a great SBC. I've assembled a number of additional components like the Joystick/Digital I/O board and the VDU too. So far, everything works except I don't know how to write to the LEDs.

I tried using WozMon to write to the same address I can read the buttons from (A000) but nothing happens -- the LEDs are just always on. Is there some direction register I have to set or something?

[tebl]

It should be fine to just do a write to that address, but I seem to remember that there was something about WozMon itself that was the issue (or a combination with something I did). Maybe try a small machine code program or something in basic. fre. 9. jul. 2021, 20:35 skrev liamoc ***@***.***>:

…

Hi, thanks for a great SBC. I've assembled a number of additional components like the Joystick/Digital I/O board and the VDU too. So far, everything works except I don't know how to write to the LEDs. I tried using WozMon to write to the same address I can read the buttons from (A000) but nothing happens -- the LEDs are just always on. Is there some direction register I have to set or something? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#21>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGEF6IMYOWLMVPJUY5HKAD3TW46QTANCNFSM5ADH7T3Q> .

[liamoc]

Hmm, I tried running this in BASIC:

> POKE -24576, 0  
> POKE -24576, 255 

And the lights remained solidly on. I think -24576 is the correct location for $A000 right? I'll try a machine code program soon.

Edit: Here's a Krusader Assembler session

? L
000        LDA #$0
001        STA $A000
002        RTS
? A
0300-0305
? R $0300

?        

Running this program doesn't seem to affect the LEDs either. I'm at a loss..

Edit: Strangely, running from $0000 does change the LEDs -- only the first one remains on. Not sure how helpful that is, but it does suggest that the CPU can talk to the LEDs in some way.

[tebl]

Now that I'm looking at the schematic, I think that the 373 should be a 374. They have the same pinouts and may have exchanged it on my board without updating the document. lør. 10. jul. 2021, 01:59 skrev liamoc ***@***.***>:

…

Hmm, I tried running this in BASIC: > POKE -24576, 0 > POKE -24576, 255 And the lights remained solidly on. I think -24576 is the correct location for $A000 right? I'll try a machine code program soon. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#21 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGEF6IKFJ7JFG62DA7BJFPDTW6EP7ANCNFSM5ADH7T3Q> .

[liamoc]

Alright, I've ordered some 374's. When they arrive I'll see what happens.

[liamoc]

This worked! So it should be 74LS374 rather than 74LS373.