MMC/SD Host Controller
7-131
MPU Public Peripherals
Table 7–98. MMC System Configuration Register (MMC_CON)
Bit
Name
Description
15
DW
Data bus width
14
Reserved
13–12
Mode
Operating mode select (MMC/SD, SPI, SYSTEST, or MMC SPI protocol).
11
Power-up
Power-up control
10 –8
Reserved
7 –0
Clk_div
Clock divider [No clock, 1:255]
Bus Width During Data Phase (DW)
SD card only.
This bit (15) must be set following a valid SET_BUS_WIDTH command
(ACMD6) with the value written in bit [1] of the argument. Prior to this
command, the SD card configuration register (SCR) must be verified for the
supported bus width by the SD card.
-
0: 1-bit data width (DAT[0] used)
-
1: 4-bit data width (DAT[3:0] used—SD card only).
Value after reset is low.
This bit must always be set to 0 for MMC cards or during SPI transfer. Not set-
ting this bit correctly can result in an unpredictable behavior.
Mode Select (Mode)
These bits (13-12) select between MMC/SD mode, SPI mode 1, SYSTEST
mode and SPI mode 2.
In MMC/SD mode, transfers to the MMC/SD card follow the MMC protocol.
MMC clock is enabled and the SPI clock is disabled.
In SPI mode1, transfers to up to three SPI controlled devices (serial flash, etc.)
are supported. In this mode, SPI clock is enabled and MMC clock is disabled.
In SYSTEST mode, the signal pins are configured as general-purpose input/
output and the 64-byte FIFO is configured as a stack memory accessible only
by the local host. The pins retain their default type (input, output or in/out).