[U-Boot-Users] [slightly offtopic] IDE interface for MPC823?
I apologize in advance. I know this is slightly offtopic here, but I think this mailing list is the closest I could get to finding someone who can answer this:
I'm looking for a schematic drawing showing how to build an IDE interface for the MPC823. I have an existing board I want to hack an IDE interface to.
I've been seaqrching the net for boards that contains an MPC823 with an IDE interface, but I couldn't come up with either an appnote, or an existing schematic. (I found a block diagram of the terrapin mine, but it wasn't a full schematic, and anyhow the IDE interface is implemented there using an FPGA).
I understand I must buffer the data bus (what type of 74xxx245 can I use? HC? HCT? something else? IIRC the IDE bus works on +5V, while the MPC823 works on 3.3V.
The PIO part seems relatively easy (I either sacrifice 2 chip selects or generate them from 1 CS using discrete gates I guess). What about DMA?
thanks, Udi
Udi Finkelstein wrote:
schematic, and anyhow the IDE interface is implemented there using an FPGA).
No FPGA needed. IDE can be implemented via PCMCIA interface.
I understand I must buffer the data bus (what type of 74xxx245 can I use? HC? HCT? something else? IIRC the IDE bus works on +5V, while the MPC823 works on 3.3V.
We use 74LCX16245 buffers for this. And a couple of gates (two NANDs exactly) to control them. They are 5V tolerant and generate 3V3 signals - no problems until now. But the serial dumping resitors (47-100 ohms) are obligatory (at least for LCX buffers). Otherwise your IDE devices will behave errorenously on longer cable. Several types of hardrives, CDROMs and Compact Flash cards connected. For more inspiration, see schematic of MPC5200 (has built-in IDE interface) Motorola evaluation board (I do not know its exact name).
The PIO part seems relatively easy (I either sacrifice 2 chip selects or generate them from 1 CS using discrete gates I guess). What about DMA?
Use CS6, CS7 in PCMCIA mode. No experiences with IDE DMA on MPC823.
Cincerelly, Jan Damborsky
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Jan Damborsky -
Udi Finkelstein