Z80 Retro #20 - SD Card Driver Block Read & Write

The github repo seen in this video:

Related project hardware repos:

A Hackaday page for Z80 Retro! projects:

Related Wikipedia pages:

Simplified SD card specification (you want Part-1):

#Z80
#SDcard
#CPM
#homebrew
#retrocomputer

[alken]

really thanks for deciphering all the sdcard commands magic and required delays, huge work!

[randallrouth]

I will admit that I have not written Z80 assembly code since may TRS-80 Model I Level I days, loading EDTASM off cassette tapes. (1981). And I do not know what you have in mind for an overall design. However, I think I would have been tempted to store the 32 bit block number in the first 4 bytes of the 512 byte I/O buffer. If that is not an option for the write operation and I had control over the buffer, I would allocate 516 bytes for the buffer and make the block address the first 4 bytes. Then pass the buffer address in the HL register pair. It would save a lot of mucking about with the stack.
I follow your videos with great interest.
Thank you.

[JohnDlugosz]

In waiting while busy after a block write:
Doesn't spi_ssel_true eat a few clocks after changing the actual ssel line, before returning?
What if the "finished" response occurs during that?
More generally, the same thing when turning ssel false first. Is it required to cycle ssel before the busy response will be sent, or is that just how all your commands are encapsulated?

[jackrubin]

Never sure whether to approach these sessions with a cup of coffee or a glass of scotch. Very happy to leave 8 bit/32 bit multi-endian hand waving to a pro. Just looking forward to seeing an A> prompt at this point!

[dietrichsimon]

hallo
thanks for your phantastic videos and super explications of the z80 board.
but can you please make a video how to order the boards by jlcpcb, which files i have to send. in zip or rar format? etc.
thanks for all.
dietrich simon