port to MMC/SD


Unfortunately, I can't make the modules pC/FAT and pC/FFS freely accessible. However, I can give here a simplified version of the MMC/SD-Card Ports on the SPI-connection for miscellaneous controller.
By using this ports you can use another FileSystem on this interface and with it accessing the MMC- and SD-Cards. Or, like my tests, a MMC/SD-to-USB adapter can be realized in software. This works like an USB-Device as MassStorage (removable media) on the PC and you have access to the MMC- and SD-cards like an professional adapter in hardware (only slower, since SPI-mode and software realization).

Here a overview over the SD-Card versions:

SD card versions

Restrictions of the simplified MMC/SD-ports:
- no interrupt- or DMA-mode
- no detailed media infos
- no read / write in call-back mode
- no direct RTOS-support

download simplified pC/FAT Ports to MMC/SD (as ZIP)
(with MMCplus/HD-MMC/M-Bridge/SDHC/SDXC support)
(with optional McEx/ASSD-support)

On a porting to further controllers, additional to the SPI-speed adaptation only some parameters of the hardware must be known and to setup. This are the used PIO-pins for WP (WriteProtect), CD (CardDetect) plus the correct settings for MOSI, MISO, SCLK and /SS. Additional the matching SPI-mode 3 must be enabled.


to used SPI-mode of the controller (master)
Following diagram shows the SPI-mode, that is required for the communication with MMC- and SD-cards in the SPI-mode:


To the topic "speed"
In the following table, all important parameters of here present MMC/MMCplus/M-Bridge/SD/SDHC-cards are listed as confrontation. This illustrates quite well that the performance statements of the manufacturers speed for MMC/SD-mode is only indirect/relative with the context in SPI-mode.
The paramters Nac and Nbs are from special interest.
- Nac = maximum cycles between Read_CMD and data
- Nbs = maximum cycles between Write_CMD+data and End-of-Busy
These parameters partly fluctuate very strongly between the different cards/manufacturers. They give an information about how fast read and write of the internal storage can be really. BUT! also these values represent the respective absolute maximum-worth. That is but also on the other hand, a card with high Nbs nevertheless can possibly be faster ready with a Write-CMD, as a card with lower Nbs. However yields these statements a tendency over the cycles at most possible/expected/permissible from the respective manufacturer.

 
 
Card
MMC
16MB

Infineon
MMC
32MB

Infineon
MMC
64MB

Transcend
MMC
128MB

SanDisk
MMC
1GB

Hama
MMCmicro
512MB

X4store
RS-MMC
32MB

SanDisk
MMCmobile
64MB

Transcend
MID-OID
01-0000
01-0000
06-0000
02-0000
48-FFFF
6F-0000
02-0000
2C-0000
maxclk
20MHz
20MHz
20MHz
20MHz
20MHz
20MHz
20MHz
20(26)MHz
usedclk*
8MHz
8MHz
8MHz
8MHz
8MHz
8MHz
8MHz
8MHz
Nac
10.012
10.012
10.012
10.012
800.000
50.000
100.000
50.000
Nbs
40.048
40.048
40.048
40.048
102.400.000
1.600.000
400.000
1.600.000
maxsectors
31.424
62.720
125.440
250.880
2.007.040
1.003.520
62720
125.440
sectorsize
512
512
512
512
512
512
512
512

 
Card
MMCmobile
512MB

Transcend
MMCmobile
1GB

extreme
MMCmobile
2GB
green
memory
MMCmobile
2GB

Kingston
MMCplus
512MB

Transcend
MMC
1GB

extreme
MMCplus
2GB

Transcend
MMCplus
4GB

Pretec
MID-OID
15-0000
00-0000
6F-0000
70-0000
1E-FFFF
4B-4342
1E-FFFF
19-5944
maxclk
20(26)MHz
20MHz
20(52)MHz
20(52)MHz
20(52)MHz
20(?)MHz
20(52)MHz
20(52)MHz
usedclk*
8MHz
8MHz
8MHz
8MHz
8MHz
8MHz
8MHz
8MHz
Nac
15.012
30.000
10.000
200.012
50.000
35.000
200.000
200.012
Nbs
1.921.536
480.000
1.280.000
25.601.536
1.600.000
1.120.000
6.400.000
25.601.536
maxsectors
1.003.520
1.935.360
1.945.600
1.983.488
990.208
2.022.912
1.981.952
1.988.096
sectorsize
512
512
1024
1024
512
512
1024
2048