User Manual
Table Of Contents
FN-LINK TECHNOLOGY LIMITED
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3.4 SDIO Interface Power-On Sequence
After power-on, the SDIO interface is selected by the RTL8723BS automatically when a valid SDIO
command is received. To attain better SDIO host compatibility, the following power-on sequence is
Recommended.
F
igure 3. SDIO Interface Power-On Sequence
SDIO Interface Power-On Sequence
S
ymbol
D
escription
T33ramp’
3.3V Power Pre-Charge Ramp Up Duration Before Formal Power Up.
We recommend that a 3.3V power-on and then power-off sequence is
executed by the host controller before the formal power on sequence. This
procedure can eliminate host card detection issues when power ramp up
duration is too long, or when a system warm reboot fails.
Toff
The duration 3.3V is cut off before formal power up.
T33ramp
The 3.3V main power ramp up duration.
T12ramp
The internal 1.2V ramp up duration.
TPOR
The duration from when the power-on reset releases and the power
management unit executes power on tasks. A power on reset will detect both
3.3V and 1.2V power ramp up after a predetermined duration.
Tnon_rdy
SDIO Not Ready Duration.
In this state, the RTL8723BS-VD may respond to commands without the ready
bit being set. After the
ready bit is set, the host will initiate complete card detection procedure.
We recommend that the card detection procedures are divided into two phases: A 3.3V power
pre-charge phase and a formal power-up phase.
During the 3.3V power pre-charge phase, the power ramp up duration is not limited. The 3.3V power is
cut off and is turned on after the Toff period. The ramp up time is specified in the T33ramp duration.
After main 3.3V ramp up and 1.2V ramp up, the power management unit is enabled by the power ready
detection circuit. The power management unit enables the SDIO block. eFUSE is then autoloaded to
SDIO circuits during the Tnon_rdy duration. After the autoload has completed, the SDIO sets the ready
bit. After CMD5/5/3/7 procedures, card detection is executed. When the driver has loaded, normal
CMD52 and CMD53 are used.