GD32W51x User Manual
761
23.4.
SDIO functional description
The following figure shows the SDIO structure. There have two main parts:
The SDIO adapter block consists of control unit which manage clock, command unit
which manage command transfer, data unit which manage data transfer.
The APB interface block contains access registers by APB2 bus, contains FIFO unit
which is data FIFO used for data transfer, and generates interrupt and DMA request
signals.
Figure 23-6. SDIO block diagram
SDIO controller
PCLK2
SDIO CLK
SDIO_CMD
SDIO_CK
SDIO_D[7:0]
SDIO adapter
control unit
comm and
unit
data uni t
regi sters
FIFO
APB interface
interrupt
DMA r equest
APB bus
23.4.1.
SDIO adapter
The SDIO adapter contains control unit, command unit and data unit, and generates signals
to cards. The signals is descript bellow:
SDIO_CK
: The SDIO_CK is the clock provided to the card. Each cycle of this signal directs a
one bit transfer on the command line (SDIO_CMD) and on all the data lines (SDIO_D). The
SDIO_CK frequency can vary between 0 MHz and 20 MHz for a Multimedia Card V3.31,
between 0 and 48 MHz for a Multimedia Card V4.2, or between 0 and 25 MHz for an SD/SD
I/O card.
The SDIO uses two clock signals: SDIO adapter clock (SDIOCK
≤
48MHz) and APB2 bus
clock (PCLK2)
The frequency of PCLK2 must be no less than the 3/8 frequency of SDIO_CK.
SDIO_CMD
: This signal is a bidirectional command channel used for card initialization and
transfer of commands. Commands are sent from the SDIO controller to the card and
responses are sent from the card to the host. The CMD signal has two operation modes: