Samsung S3C2451X User Manual page 474

HSMMC CONTROLLER
SD BUS POWER CONTROL SEQUENCE
The sequence for controlling the SD Bus Power is described in Figure 21-6.
(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.
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
21-6
Specifications and information herein are subject to change without notice.
(1)
Get the support voltage of the
(2)
Set SD Bus voltage select with
supported maximum voltage
(3)
Set SD Bus Power
(4)
Get OCR value of the SD Card
(5)
no change
(6)
Clr SD Bus Power
(7)
Set SD Bus voltage select
(8)
Set SD Bus Power
Figure 21-6 SD Bus Power Control Sequence
S3C2451X RISC MICROPROCESSOR
START
Host Controller
SD Bus voltage
changed ?
change
END