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below. A card will complete the command within
this time period or give up and return an error
message. If the host does not get a response within
the defined time-out, it should assume the card is
not going to respond any more and try to recover
(e.g. reset the card, power cycle, reject, etc.). The
typical access and program times are defined as
follows:
Read
The read access time is defined as the sum of t h e
two times given by the CSD parameters TAAC
and NSAC. These card parameters define t h e
typical delay between the end bit of the read
command and the start bit of the data block. This
number is card dependent and should be used by
the
host to calculate
maximum frequency for stream read.
6.2
SPI Command Set
6.2.1
Command Format
All the MultiMediaCard commands are 6 bytes
long and transmitted MSB first.
Byte 1
7
6
5
0
1
Command
Commands and arguments are listed in Table 6-4.
7-bit CRC Calculation: G(x) = x
39
M(x) = (start bit) x
+ (host bit) x
CRC[6...0] = Remainder[(M(x) x
SanDisk MultiMediaCard Product Manual Rev. 2 © 2000 SANDISK CORPORATION
throughput
and t h e
Bytes 2 - 5
0
31
Command Argument
7 +
3 +
x
1
38
+...+ (last bit before CRC) x
7
)/G(x)]
MultiMediaCard Product Manual
Write
The R2W_FACTOR field in the CSD is used to
calculate the typical block program time obtained
by multiplying the read access time by this factor.
It applies to all write/erase commands (e.g. SET
(CLEAR)_WRITE_PROTECT,
(CID) and the block write commands). It should be
used by the host to calculate throughput and t h e
maximum frequency for stream write.
Erase
The duration of an erase command will be (order of
magnitude) the number of sectors to be erased
multiplied by the block write delay.
6.1.10 Memory Array Partitioning
Same as for MultiMediaCard mode.
0
0
PROGRAM_CSD
Byte 6
7
CRC
0
1
65
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