Espressif ESP32 Technical Reference Manual page 194

9 SD/MMC Host Controller
9 SD/MMC Host Controller
9.1 Overview
The ESP32 memory card interface controller provides a hardware interface between the Advanced Peripheral
Bus (APB) and an external memory device. The memory card interface allows the ESP32 to be connected to
SDIO memory cards, MMC cards and devices with a CE-ATA interface. It supports two external cards (Card0
and Card1).
9.2 Features
This module has the following features:
• Two external cards
• Supports SD Memory Card standard: versions 3.0 and 3.01
• Supports MMC: versions 4.41, 4.5, and 4.51
• Supports CE-ATA: version 1.1
• Supports 1-bit, 4-bit, and 8-bit (Card0 only) modes
The SD/MMC controller topology is shown in Figure 9-1. The controller supports two peripherals which cannot
be functional at the same time.
9.3 SD/MMC External Interface Signals
The primary external interface signals, which enable the SD/MMC controller to communicate with an external
device, are clock (clk), command (cmd) and data signals. Additional signals include the card interrupt, card
detect, and write-protect signals. The direction of each signal is shown in Figure 9-2. The direction and de-
scription of each pin are listed in Table 9-1.
Espressif Systems
Figure 9-1. SD/MMC Controller Topology
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