Specifications

Physical Layer Simplified Specification Version 4.10

4. SD Memory Card Functional Description

4.1 General

All communication between host and cards is controlled by the host (master). The host sends com-

mands of two types: broadcast and addressed (point-to-point) commands.

• Broadcast commands

Broadcast commands are intended for all cards. Some of these commands require a response.

• Addressed (point-to-point) commands

The addressed commands are sent to the addressed card and cause a response from this card.

A general overview of the command flow is shown in Figure 4-1 for card identification mode and in

Figure 4-13 for data transfer mode. The commands are listed in the command tables (Table 4-22-

Table 4-31). The dependencies between current state, received command, and following state are

listed in Table 4-34. In the following sections, the various card operation modes will be described

first. Afterwards, the restrictions for controlling the clock signal are defined. All SD Memory Card

commands, along with the corresponding responses, state transitions, error conditions and timings

are presented in the succeeding sections.

Two operation modes are defined for the SD Memory Card system (host and cards):

• Card identification mode

The host will be in card identification mode after reset and while it is looking for new cards on the

bus. Cards will be in this mode after reset until the SEND_RCA command (CMD3) is received.

• Data transfer mode

Cards will enter data transfer mode after their RCA is first published. The host will enter data

transfer mode after identifying all the cards on the bus.

The following table shows the dependencies between operation modes and card states. Each state in

the SD Memory Card state diagram (see Figure 4-1) is associated with one operation mode:

Card state

Operation mode

Inactive State

inactive

Idle State

card identification mode

Ready State

Identification State

Stand-by State

data transfer mode

Transfer State

Sending-data State

Receive-data State

Programming State

Disconnect State

Table 4-1: Overview of Card States vs. Operation Modes