Hello,

Have some make a hard- and software part to connect the 6502 uP to a SD-Card?

Rg
Softboy1

I have an MMFS setup on my BBC micro, courtesy of Dave (hoglet) - it uses a parallel port (VIA) to communicate with a little commodity SD card interface board.

I think it's quite possible to bitbang the whole protocol but you'll probably need level shifting.

Here's an example on a PC - the principle is the same, of course how to drive the parallel port is different:
http://blog.vinu.co.in/2012/05/attempt- ... ed-at.html

You could as well implement a IDE interface and use one of the IDE to SD card or IDE to CF-Card Adapters. IDE can be implemented with a W65C22. CF-Card Adapters have the advantage that the CF-Card Adapter is only electrically passing the signals from the IDE to the CF-Card, that is there is no dealy. As CF-Cards (at least the 5V capable CF-Cards with only a few Gbytes of Memory) support a 8-bit IDE mode you only need a 8-bit data bus. In this case you only need to connect D0..7 and A0..A2 from the 6502 to the IDE port and add some glue logic to create /IORD, /IOWR and /CS0 (you don't need /CS1) and of course /RESET and you would not even need a interface device like the W65C22. I have connected CF-Cards directly to the CPU bus with CPU clocks up to 8MHz and it works.

Another example of hooking up an SD-Card to a 6502-based computer:
https://steckschwein.de/hardware/via-65 ... i-devices/

SPI is bit banged using a VIA, a 74ls07 is used for level shifting.

My hobby / project is a 6502 homebrew machine with video (TMS9918), sound (AY-3-8910) and relevant for you an SD Card interface driving a hobbytronics SD card breakout board. This simple but compact board provides a slot for a micro SD card, and exposes the lines needed to drive the SPIO interface (CLK, DO, DI, CS, CD). The SPIO lines are connected to a 6522 and so all transfers are bit-banged in software. Not massively fast but still getting around 8.5k per second which is enough for my needs.

https://hackaday.io/project/5789-6502-homebrew-computer/log/26703-sd-card-interface

My main site includes the sd card driver code, but also the FAT16 routines which are much more complicated but allows a standard PC-DOS format to be used which can be helpful in portability.

Hope this helps.

I have done some SPI interfaces for the 6502.

1) an SPI interface card using a CPLD as bus->SPI interface, connecting an SD-Card, Ethernet and USB chips via SPI: http://www.6502.org/users/andre/csa/netusb/index.html using this CPLD: http://www.6502.org/users/andre/spi65b/index.html

2) An SPI-based USB-interface for the Commodore userport: http://www.6502.org/users/andre/cbmhw/cbmusb/index.html

3) An SD-Card interface using the VIA shift register (almost) only: http://www.6502.org/users/andre/csa/spi/index.html (yes it works

General SPI info: http://www.6502.org/users/andre/hwinfo/spi/index.html

BTW: I would rather now build an USB interface for example to an USB memory stick. It's much more flexible than SD-Card nowadays...

_________________
Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

Kudos for the USB-capable PET! In the land of Acorn, there are both SD-Card and USB storage solutions using the VIA, but it seems to me that SD is winning. Of course, beyond storage, or for huge capacity, USB offers lots of other possibilities. (I note that your USB solution actually starts off as SPI - perhaps SPI is the great universal interface for the 8-bit micro. The Maxim MAX3420 and MAX3421 seem to be very handy. "The MAX3421E is a USB controller that can function either as a USB peripheral or host. It builds on Maxim's MAX3420E peripheral-only controller")

One of my products for the BBC Micro incorporates an SD interface : http://www.zeridajh.org/hardware/gosdc/index.htm. It allows the 6502 to do simple byte reads/writes, the hardware in the CPLD does the serial <-> parallel conversions (based on its own clock). Well, it's an SPI interface, really, i.e. it also talks to MMC (that's how it started) and the serial flash ROM on GoSDC.

Doing it properly requires some careful design, but it's quite doable.