Samsung S5PC110 Manual page 984

S5PC110_UM
7.4.2 SD CLOCK SUPPLY SEQUENCE
The sequence to set SD Clock to a SD card is shown in
following actions:
−
a) Issuing a SD command
−
b) Detect an interrupt from a SD card in 4-bit mode.
The steps to set SD Clock to a SD card:
1. Calculate a divisor to determine SD Clock frequency for SD Clock by reading Base Clock Frequency.
Refer to clock control register (9.15).
2. Set Internal Clock Enable (ENINTCLK) and SDCLK Frequency Select in the Clock Control register in
accordance with the calculated result of step (1).
3. Check Internal Clock Stable (STBLINTCLK) in the Clock Control register. Repeat this step until Clock
Stable is 1.
4. Set SD Clock Enable (ENSDCLK) in the Clock Control register to 1. After ENSDCLK is set, the Host
Controller starts SD Clock.
Figure 7-3 SD Clock Supply Sequence
Figure 7-3
. The clock is enabled before one of the
7 SD/MMC CONTROLLER
7-4