Re: [N8VEM-S100:7701] SD Card Questions

[Max Scane <mjs...@gmail.com>]

Hi John,

Why keep the 8255?  It was really only needed to support 16 bit IDE interfaces.  Most people only want to use Compact Flash these days and all Compact Flash cards support 8 bit mode.  If you really need 16 bit compatibility replicate the GIDE with a couple of GALS and registers.

You can directly connect the CF card to the IO bus and program it for 8 bit mode. You will find it much faster.  The N8VEM M4 processor card has both an 8 bit CF and an SD card.  The SD card uses the CSI interface of the Z180 for SPI serial but is still much slower than the Compact Flash drive.

SD cards are a bit more tricky and require more processing and protocol overhead.  Depending on where you do all that processing it would be slower than a IDE.  You would need to pass off the SD card protocol and SPI interface to a separate micro I think.  Bit banging the SPI connection to the SD card is quite slow.

Cheers!

Max

On Thu, Oct 1, 2015 at 10:13 PM, John Monahan <mon...@vitasoft.org> wrote:

Hi Josh,

I am toying with the idea of building a dual Micro SD card S100 board.  I’m finding that the bottleneck in my 80386/80486 prototypes for MSDOS etc. is the 8255A driven dual IDE/CF board.  Did you get the SD card working with CP/M on your 8080 board.  Any idea how “fast” it is relative to a CF card for data access.   I’m worried the interface is in fact slower that an 8255A.  Perhaps a large Flash RAM board would be a better approach. What do you think.

 

John

 

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