User Manual

Secure Digital (SD) Bus Protocol Description
4-18 TriFlash with SD Interface Product Manual (Preliminary), Rev. 1.2 © 2002/2003 SANDISK CORPORATION
4.8.1. Command Types
There are four kinds of commands defined to control the TriFlash:
• 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 device will accept it separately
on his turn.
• Broadcast Commands with Response (bcr)—response from all devices simultaneously. Since there
is no Open Drain mode in TriFlash, this type of command is used only if all the CMD lines are
separated. The command will be accepted and responded to by every device 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 TriFlash. The command transmission always starts
with the left bit of the bit string corresponding to the command code word.
4.8.2. Command Format
The Command length is 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
1
end bit
Commands and arguments are listed in Table 4-4 through Table 4-11.
7-bit CRC Calculation: G(x) = x
7
+ x
3
+ 1
M(x) = (start bit)∗x
39
+ (host bit)∗x
38
+...+ (last bit before CRC)∗x
0
CRC[6...0] = Remainder[(M(x)∗x
7
)/G(x)]
4.8.3. Command Classes
The command set of the TriFlash is divided into several classes (refer to Table 4-3). Each class supports a set of SD
functions.
The supported Card Command Classes (CCC) are coded as a parameter in the card specific data (CSD) register of
each device, providing the host with information on how to access the device.
1
7-bit Cyclic Redundancy Check.