Sd Bus Power Control Sequence - Samsung S3C2416 User Manual

HSMMC CONTROLLER

4.5 SD BUS POWER CONTROL SEQUENCE

The sequence for controlling the SD Bus Power is described in Figure 20-6.
(1) By reading the Capabilities register, get the support voltage of the Host Controller.
(2) Set SD Bus Voltage Select in the Power Control register 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 needs to be changed or not. In case where SD Bus voltage needs to be
changed, go to step (6). In case where SD Bus voltage does not need 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 shall clear 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. And also, step (7) and step (8) can be executed at same time.
20-6
(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 20-6. SD Bus Power Control Sequence
START
Host Controller
Set SD Bus Power
SD Bus voltage
changed ?
change
Clr SD Bus Power
Set SD Bus Power
END
S3C2416X RISC MICROPROCESSOR