Commodore 64 IRQ Bicolor LED
Ho trovato questo vecchio progetto pubblicato su una rivista olandese, serve per acquisire e visualizzare lo stato dell’IRQ per Commodore 64 (Vic-20) con un LED. Dopo molti anni ho deciso di metterlo in pratica.
Nelle foto potete vedere il progetto e le giuste connessioni sulla porta cartuccia.
Componenti :
- 1 x IC 74LS04.
- 1 x Bicolor LED.
- 2 x resistenze da 330 ohm.
- Cavo elettrico.
Come funziona?
Quando la CPU genera un IRQ il LED verde si accende, altrimenti rimane rosso, se l’IRQ viene acceso e spento velocemente il led è arancione.
The bicolor LED I bought at Radio Shack (part: 276-0012) only had two leads, not three. To make this work with the schematic, simply skip the connection from GND to the middle lead of the LED, as it doesn’t exist.
Certain c64 applications (eg.GEOS) cause the LED to stay orange (turning on/off very fast). I don’t like the look of the orange, so I wanted a simple way to turn the effect on/off that didn’t involve opening the c64. This can be achieved by either:
1) Adding a 330Ohm resistor in between the IRQ line and pin 1 of the 7404 and then add an externally mounted SPST switch wired to short pin 1 of the 7404 to GND when closed. Shorting to ground overrides the IRQ signal, leaving the LED red.
2) Adding an externally mounted SPDT switch, connecting the middle pin of the switch to pin 1 of the 7404 then one of the other switch pins to the IRQ line and the last switch pin to GND. The switch now chooses what is connected to pin 1; IRQ or GND.
Cheers!
-=Randy
This is a great mod for the 64 and we have made a small plug in PCB, have a look at -
http://blog.sharewareplus.co.uk/
@Tim Harris
Hi Tim, you have made a nice work!.
Can, someone share pcb design