ARM External Bus Controller Timing

[SimonR]

Thats brilliant, thanky so much for doing that. I might get an ST32 dev board and do some testing.

Amazing an application processor out gunned by an embedded  one.

That processor was picked for its CF card interface, external bus and on boarf FLASH/SRAM. Thats all we needed, although we do use the ethernet now as well.
You would have thougkt that a 5 nS instruction cycle would be more than enough, and actually it is if you have a good bus controller.

[knielsen]

As another option, have you considered bit-banging the external bus? Since you already need to bit-bang the REQ/ACK, maybe doing the whole bus protocol yourself would be a reasonable option. This is assuming that your CPU can do GPIO in few tens of nanoseconds, and that your hardware pinout makes it possible, of course...

 - Kristian.

[SimonR]

I did consider that that, I think the GPIO lines are more than fast enough, because I already use them for the DMA signals. The trouble is the Address and Data busses are completely seperate from the GPIO lines so it would be a board re-spin.

[krho]

According to the manual STM32F4xxx famil with external FSMC also has a support for CF cards.

36.6.7 PC Card/CompactFlash operations
The FSMC supports Compact Flash storage or PC Cards in Memory Mode and I/O Mode
(True IDE mode is not supported).

[SimonR]

According to the manual STM32F4xxx famil with external FSMC also has a support for CF cards.

That makes it even more interesting