7. eMMC Functional Description

7.1 eMMC Overview

All communication between host and device are controlled by the host (master). The host sends a command,

which results in a device response. For more details, refer to section 6.1 of the JEDEC Standard JESD84-B51.

Five operation modes are defined for the eMMC system:



Boot operation mode



Device identification mode



Interrupt mode



Data transfer mode



Inactive mode

7.2 Boot Operation Mode

In boot operation mode, the master (eMMC host) can read boot data from the slave (eMMC device) by keeping

CMD line low or sending CMD0 with argument + 0xFFFFFFFA, before issuing CMD1. The data can be read from

either boot area or user area depending on register setting. For more details, refer to section 6.3 of the JEDEC

Standard JESD84-B51.

7.3 Device Identification Mode

While in device identification mode the host resets the device, validates operation voltage range and access

mode, identifies the device and assigns a Relative device Address (RCA) to the device on the bus. All data

communication in the Device Identification Mode uses the command line (CMD) only. For more details, refer

to section 6.4 of the JEDEC Standard JESD84-B51.

7.4 Interrupt Mode

The interrupt mode on the eMMC system enables the master (eMMC host) to grant the transmission allowance

to the slaves (Device) simultaneously. This mode reduces the polling load for the host and hence, the power

consumption of the system, while maintaining adequate responsiveness of the host to a Device request for

service. Supporting eMMC interrupt mode is an option, both for the host and the Device. For more details,

refer to section 6.5 of the JEDEC Standard JESD84-B51.

7.5 Data Transfer Mode

When the Device is in

Stand-by State, communication over the CMD and DAT lines will be performed in push-

pull mode. For more details, refer to section 6.6 of the JEDEC Standard JESD84-B51.

7.6 Inactive Mode

The device will enter inactive mode if either the device operating voltage range or access mode is not valid.

The device can also enter inactive mode with GO_INACTIVE_STATE command (CMD15). The device will reset to

Pre-idle state with power cycle. For more details, refer to section 6.1 of the JEDEC Standard JESD84-B51.

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