Samsung S5PC100 User Manual page 941

SD/MMC CONTROLLER
4.5 SD BUS POWER CONTROL SEQUENCE
The sequence for controlling the SD Bus Power is shown in Figure 8.12-6 and steps are described below:
(1) Read the Capabilities register, to get the support voltage of the Host Controller.
(2) Set SD Bus Voltage Select in external power regulator (optional) with maximum voltage that the Host
Controller supports.
(3) Set SD Bus Power (PWRON) in the Power Control register to 1.
(4) Get the OCR value of all function internal of SD card.
(5) Judge whether SD Bus voltage must be changed or not. If SD Bus voltage must be changed, continue with
step (6). If SD Bus voltage is not to be changed, go to 'End'.
(6) Set SD Bus Power in the Power Control register to 0 for clearing this bit. The card requires voltage rising from
0 volt to detect it correctly. The Host Driver clears SD Bus Power before changing voltage by setting SD Bus
Voltage Select.
(7) Set SD Bus Voltage Select (SELPWRLVL) in the Power Control register.
(8) Set SD Bus Power (PWRON) in the Power Control register to 1.
NOTE: Step (2) and step (3) can be executed at same time. Also, step (7) and step (8) can be executed at same time.
8.12-6
(1)
Get the support voltage of the
(2)
Set SD Bus voltage select with
supported maximum voltage
(3)
(4)
Get OCR value of the SD Card
(5)
no change
(6)
(7)
Set SD Bus voltage select
(8)
Figure 8.12-6 SD Bus Power Control Sequence
START
Host Controller
Set SD Bus Power
SD Bus voltage
changed ?
change
Clear SD Bus Power
Set SD Bus Power
END
S5PC100 USER'S MANUAL (REV1.0)