SanDisk SDSDB-32-201-80 - Industrial Grade Flash Memory Card Manual download pdf (Page 70)

Secure Digital (SD) Card Protocol Description

4.8. Commands

The following sections provide valuable information on commands.

4.8.1. Command Types

There are four kinds of commands defined to control the Industrial Grade 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 Industrial Grade 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 Industrial Grade 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 µs @ 25 MHz)

0 1 bit 5...bit 0 bit 31...bit 0 bit 6...bit 0 1

start bit host command argument CRC7

end bit

Commands and arguments are listed in Table 5-3 through Table 5-10.

7-bit CRC Calculation: G(x) = x

7 +

3 +

M(x) = (start bit)∗x

+ (host bit)∗x

+...+ (last bit before CRC)∗x

CRC[6...0] = Remainder[(M(x)∗x

)/G(x)]

4.8.3. Command Classes

The command set of the Industrial Grade 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.

1 2 ... 65 66 67 68 69 70 71 72 73 74 75 ... 118 119

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SanDisk SDSDB-32-201-80 - Industrial Grade Flash Memory Card Manual Page 70