> 48mhz PIC is too > fast, or maybe it's my breadboard... That's what I happened to work on today ;-)
It is to fast for drives that do not support PIO modes 3 or 4. I have a drive that works at 32MHz without the delay and one that doesn't. However, to really use PIO modes 3 and 4, IORDY needs to be observed to see if the disk really has valid data on the bus. Even if IORDY indicates valid data, just the check would consume far more time than just unconditionally executing the "nop", so it would be futile to try to use those modes. The PIO data transfer timings in the standard documents are somewhat confusing, but I guess to be on the safe side, one should wait 260ns after assertion of /DIOR. >From PIF18F4520 datasheet you can read that the time between a port write and a port read is at minimum about 1.25Tcy. Based on these numbers, you would need 1 nop from 16MHz 2 nop from 34MHz 3 nop from 50MHz 4 nop from 64MHz (as soon as there are PIC18 that can :-) Greets, Kiste -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
