Command Types; Command Format; Command Classes - SanDisk SDSDB-32-201-80 - Industrial Grade Flash Memory Card Product Manual

Secure Digital (SD) Card Protocol Description

4.8.1. Command Types

There are four kinds of commands defined to control the SD Card:
Broadcast Commands (bc), no response—The broadcast feature is applicable only if all the CMD lines
are connected together in the host. If they are separated then each card will accept it separately on his
turn.
Broadcast Commands with Response (bcr)—response from all cards simultaneously. Since there is no
Open Drain mode in SD Card, this type of command is used only if all the CMD lines are separated.
The command will be accepted and responded to by every card separately.
Addressed (point-to-point) Commands (ac)—no data transfer on DAT.
Addressed (point-to-point) Data Transfer Commands (adtc)—data transfer on DAT.
All commands and responses are sent over the CMD line of the SD Card. The command transmission always starts
with the left bit of the bit string corresponding to the command code word.

4.8.2. Command Format

(Command length 48 bits, 1.92 s @ 25 MHz)
0 1
start bit host
Commands and arguments are listed in Table 5-3 through Table 5-10.
7-bit CRC Calculation: G(x) = x
39
M(x) = (start bit) x + (host bit) x
CRC[6...0] = Remainder[(M(x) x

4.8.3. Command Classes

The command set of the SD Card is divided into several classes (refer to Figure 4-2). Each class supports a set of
SD Card functions.
The supported Card Command Classes (CCC) are coded as a parameter in the card specific data (CSD) register of
each card, providing the host with information on how to access the card.
1) 7-bit Cyclic Redundancy Check.
4-18
bit 5...bit 0 bit 31...bit 0
command argument
7 + 3 +
x 1
38
+...+ (last bit before CRC) x
7
)/G(x)]
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
bit 6...bit 0
CRC7 end bit
1
0
1