vincelee@tornado.Berkeley.EDU (Vincent H. Lee) (03/16/91)
Well, after a day of experimenting, I have reached some conclusions about why the pd io board's parallel port won't work with my lucas board. 1) Software problem. I recompiled the "partest" program and, after adding a few NOP's to the main loop, got it to work perfectly. Apparently, the VIA doesn't like to get output too soon after its flag register has been read. This fixes the partest program, but this method doesn't completely fix eightbit.device, which locks up when printing a file more than a few lines. This seems to be due to a second problem. 2) Weird hardware problem For some really strange reason, the VIA's Peripheral Control Reg and Interrupt Enable registers don't hold their values. For instance, if I put 0x82 in IER and 0xaa in PCR and poll both, ier will decay to 0x80 in a second or two, while PCR might become 0x8a, then 0x82, then 0x80, and then 0. The timing and paths are diffent every time, but end states are always the same. What is going on? This will happen booting from a floppy with no software running, but will never happen in 68000 mode. HELP!!! -vince t