erd@tut.cis.ohio-state.edu (Ethan R. Dicks) (04/24/88)
I looked at the differences internally between the 6526 CIA and the 8520 CIA, and found that the only difference is in the TOD clock, one is BCD and the other is binary. I also found by looking in my AW RKM hardware manual that the TODs are used for the timer.device for 60Hz and millisecond event timers I assume that there is not a version of the 6526 which can be stuck directly on the 7.1 MHz Amiga bus, but am I wrong? Are the pinouts the same? (I could not find an 8520 pinout in _my_ literature, but then I don't have the A1000 schematics) If you could stick a 6526 in the 8520 slot, how could you replace the timer.device with one which understands a BCD timer? Note: I am not asking how to manipulate BCD with a 68000, but how to change a device driver which is _not_ disk resident. The obvious benefit _IF_ such a swap is possible, is that for owners of A1000 (since we _can_ patch Kickstart) with blown 8520s, the wait for a replacement 8520 can be shortened by using the much more readily available 6526. I do realize that I am probable blowing smoke rings here, but I have to at least pose the question, so it can be shot down completely and thouroghly. (IMHO, followups should be posted to allow all parties interested to see all the discussion) Thanks, -ethan -- Ethan R. Dicks | ###### This signifies that the poster is a member in Specialized Software| ## good sitting of Inertia House: Bodies at rest. 2101 Iuka Ave. | ## Columbus OH 43201 | ###### "You get it, you're closer."
grr@cbmvax.UUCP (George Robbins) (04/25/88)
In article <11419@tut.cis.ohio-state.edu> erd@tut.cis.ohio-state.edu (Ethan R. Dicks) writes: > > I looked at the differences internally between the 6526 CIA and the 8520 CIA, > and found that the only difference is in the TOD clock, one is BCD and the > other is binary. I also found by looking in my AW RKM hardware manual that > the TODs are used for the timer.device for 60Hz and millisecond event timers The changes addressed were as follows: 1) Change TOD counter to a binary counter w/o divide by 5/6 prescaler, including some timer bit shuffling. 2) Resolve the 6526 problem where interrupt request bits are set and can thus be unintentionally cleared one cycle prior to setting the overall interrupt request flag. 3) Provide additional delay on PC pin to meet Centronics setup/deskew spec. 4) Tighter specification of bus interface timings to match 68000 vs 6502 specs. 5) Auto-start of timers set for one-shot mode. 6) Specification of minimum timings for F and CNT inputs. > I assume that there is not a version of the 6526 which can be stuck directly > on the 7.1 MHz Amiga bus, but am I wrong? Are the pinouts the same? (I could > not find an 8520 pinout in _my_ literature, but then I don't have the A1000 > schematics) If you could stick a 6526 in the 8520 slot, how could you > replace the timer.device with one which understands a BCD timer? Note: I > am not asking how to manipulate BCD with a 68000, but how to change a device > driver which is _not_ disk resident. The pinout is the same and the various timings are probably good enough to slip by in most cases, however I wouldn't expect the software to work correctly if the two interval counters don't operate in the expected manner. It might limp along rather than croaking instantly, but I wouldn't bet on it... -- George Robbins - now working for, uucp: {uunet|ihnp4|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@uunet.uu.net Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)