Posted by Edge on 17, 2000 at 1:47 PM:
Subject line pretty much says it all.
I built two variants of the printer port hardware
(one using a 74HCT161 syncronous presettable 4-bit counter, and another using a J-K flip flop, both of which I configured to work as single-bit latches) and the darn things always default the mointor control output to "ON" when I power up the machine!
I am using the PC's power supply (via a spare HD power connector) to power the circuit. There are no available slots to add a printer card (which I've seen recommended as a kludge). I've configured the BIOS to be a "normal" parallel port (not ECP or EPP) and that still didn't make any difference.
Can any EE's out there offer any suggestions on some simple modifications that, on cold boot, would ensure that the latch outputs a "0" (monitor off)? A link to the ArcadeOS parallel port monitor control hardware is below. One thing I already tried (which isn't listed in the schematic) is connecting D7 (the input to the latch) to ground via a 1K resistor; didn't help. (Also, note that pin 10 is ACK, not pin 12 as listed on some of the ArcadeOS/PC2JAMMA pages.)
As an aside, if I had Borland C++ 3.1 I bet I could recomplile ArcadeOS and make the printer hardware requirements simpler. ArcadeOS is using regular BIOS routines (_bios_printer) to send a byte out the parallel port, which requires dealing with the whole ACK/BUSY handshake thing. If you simply wrote directly to the parallel port IO addresses with outb() you could avoid that whole portion of the circuit! See http://www.beyondlogic.org for some useful information on interfacing to the PC, including software examples.