Espressif ESP32 Technical Reference Manual page 196

9 SD/MMC Host Controller
9.4.1.1 BIU
The BIU provides the access to registers and FIFO data through the Host Interface Unit (HIU). Additionally, it
provides FIFO access to independent data through a DMA interface. The host interface can be configured
as an APB interface. Figure
functions:
• Host interface
• DMA interface
• Interrupt control
• Register access
• FIFO access
• Power/pull-up control and card detection
9.4.1.2 CIU
The CIU module implements the card-specific protocols. Within the CIU, the command path control unit and
data path control unit prompt the controller to interface with the command and data ports, respectively, of the
SD/MMC/CE-ATA cards. The CIU also provides clock control. Figure
CIU, which consists of the following primary functional blocks:
• Command path
• Data path
• SDIO interrupt control
• Clock control
• Mux/demux unit
9.4.2 Command Path
The command path performs the following functions:
Espressif Systems
Figure 9-3. SDIO Host Block Diagram
9-3 illustrates the internal components of the BIU. The BIU provides the following
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9-3 illustrates the internal structure of the
196 ESP32 TRM (Version 5.2)