cliff@jarthur.Claremont.EDU (Clifford Stein) (06/25/91)
I'm trying to hook up my Commodore 1520 plotter (the old C64 color plotter) to my ST. I've built the cable--I'm going to plug it in to my parallel port-- and now I just need to send it the proper signals. Since the C64 uses a serial data bus, I will have to send eveything bit by bit. After looking through my C64 Programmer Reference Guide, I found out the timing signals I need. The trouble is, I need to send signals 20 micro-seconds long through the parallel port. I was gonna do this through the IO port B on the sound chip but I forsee several problems: 1. Can the port handle signals this fast? After looking through my printer (centronics) manual, it looks like this shouldn't be a problem. 2. The biggie: How can I time my code for these types of signals. It looks as if I am going to have to count clock cycles. I'm trying get get my hands on a 68000 manual and haven't had much luck yet. Is there another way, possibly by using the sound chip or maybe something else to count micro-seconds or even 20 micro-second intervals? Obviously I'm doing this in assembly. If everything works right, I will hopefully patch the Bconout() bios call and provide myself with another device type. I would prefer to use my cartridge port for this type of thing so I wouldn't have to unplug my printer so often, but from what I hear it is difficult to write to the cartridge port (I know it can be done, though. There was an article in STart). Is it so bad? Once I get this working, I suppose I could even hook up my 1541. Joy! Rapture! Thanks for any help. --Clifford Stein