HB288032MM1 Datasheet, PDF (47/80 Pages) Hitachi Semiconductor – MultiMediaCard 32 MByte

HB288032MM1
• Stream read
The data transfer starts N_AC clock cycles after the end bit of the host command. The bus transaction is
identical to that of a read block command (refer to Figure “Data Read Timing”). As the data transfer is not
block-oriented, the data stream does not include the CRC checksum. Consequently the host can not check
for data validity. The data stream is terminated by a stop command. The corresponding bus transaction is
identical to the stop command for the multiple read block (refer to Figure “Timing of Stop Command”).
• Single or multiple block write
The host selects one card for data write operation by CMD7. The host sets the valid block length for block-
oriented data transfer by CMD16. The host transfers the data with CMD24. The address of the data block
is determined by the argument of this command. This command is responded by the card on the CMD line
as usual. The data transfer from the host starts N_WR clock cycles after the card response was received. The
write data have CRC check bits to allow the card to check the transferred data for transmission errors. The
card sends the CRC check information as a CRC status to the host (on the data line). The CRC status
contains the information if the write data transfer was non-erroneous (the CRC check did not fail) or not.
In the case of transmission error the card sends a negative CRC status (“101” bin) which forces the host to
retransmit the data. In the case of non-erroneous transmission the card sends a positive CRC status (“010”
bin) and starts the data programming procedure.
CMD
DAT
Host command
N_CR
Card response
S T content CRC E
Host active
S T content CRC E
Card active
N_WR
Z Z Z **** Z Z Z Z Z Z Z Z Z **** Z Z Z Z Z P S
CMD
DAT
Write data
CRC status Card busy
content
CRC E Z Z S status E S busy = 'L' E Z
Host active
Card active
Write data
content
Host active
L ... pull down to LOW bit
Timing of The Block Write Command
If the card does not have any more free data receive buffer, the card indicates it by pulling down the data
line to LOW. The card stops pulling down the data line as soon as at least one receive buffer for the
defined data transfer block length becomes free. This signalling does not give any information about the
data write status. This information has to be polled by the status polling command.
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