DEC RK07 drive interface specs wanted

Brad> "Peter C. Wallace" wrote: ... Brad> I'm designing a simple board with a PIC cpu and a CPLD which Brad> should be able to emulate virtually any disk controller (given Brad> software). Brad> The idea is that the cpld holds a register set which the PIC Brad> and unibus can read/write and the PIC can be a bus master to Brad> read/write unibus memory. That should do the job just fine for MSCP (except that this may be too large a job for a PIC). For older disk controllers, this approach is likely to be hard because touching CSRs causes actions to take place, and often actions are tied to bits, not just to the whole CSR. You may be able to emulate that in software, but it's likely to be tricky because your CPLD will have to be more than just a register file. I'd say that anything that was originally done as a microprocessor plus register file would be no problem. That means (T)MSCP devices, the DMC/DMR/DMP/DMV11 series comm controllers, the KMC11, and the Pro hard drive controller. But if it started out as hard logic, a microprocessor emulation wouldn't be as easy. That's why the programming interface style changed quite drastically when microprocessor control became interesting. paul