Co-routines was Re: [PDP8-Lovers] if you hadn't already known this about the PDP-8

"Sean 'Captain Napalm' Conner" <spc(a)conman.org> wrote: The only time I remember using a coroutine was a time when I had no interrupts to use. The Sega Genesis has a 68000 with main program memory, plus a sound system controlled by a Z80 with it's own sound memory. Sound memory is loaded with a sound driver written in Z80 assembly. Now the sound system has a free running timer but no interrupts, so most games had a sound driver that played FM sounds or a sound driver that played digitized sound. My job was to take an FM sound driver and make it play digitized sound at the same time. So I wrote a routine that quickly checked if a digitized sound was playing and if it was, then check if it was time to stuff the next value of the digitized sound. The hard part was then to pepper the existing sound driver with calls to this coroutine such that the existing sound driver would not be slowed down and that the digitized sound would be played at a constant rate. It worked great. Oh! "what, exactly is a co-routine?" A coroutine is a procedure that executes from the point it last suspended execution up to the next instruction that suspends its execution. That is, it preserves state between invocations. Regards, --Doug ========================================= Doug Coward @ home in Poulsbo, WA Analog Computer Online Museum and History Center http://www.best.com/~dcoward/analog =========================================