HB28D032MM2 datasheet(38/90 Pages) RENESAS

38 / 90 page

HB28H016/D032/B064/B128MM2

Rev.5.0, Jan. 2003, page 36 of 88

ends with an end bit (HIGH). The data transmission is synchronous to the clock signal. The payload for

block-oriented data transfer is preserved by a 16-bit CRC check sum (refer to Chapter “Cyclic Redundancy

Check (CRC)”).

• Stream read

There is a stream oriented data transfer controlled by READ_DAT_UNTIL_STOP (CMD11). This

command instructs the card to send its payload, starting at a specified address, until the host sends a

STOP_TRANSMISSION command (CMD12). The stop command has an execution delay due to the serial

command transmission. The data transfer stops after the end bit of the stop command. If the end of the

memory range is reached while sending data and no stop command has been sent yet by the host, the

contents of the further transferred payload is undefined. The maximum clock frequency for stream read

operation is given by the following formula:

max. speed = min (TRAN_SPEED, (8*2

READ_BL_LEN-NSAC)/TAAC),

= min (20, (8*2

− 100 [cycles])/1000 [µs]) [MHz]

= min (20, 3.996) 3.996 [MHz]

these parameters being defined in Chapter “Registers”. If the host attempts to use a higher frequency, the

card may not be able to sustain data transfer. If this happens, the card will set the UNDERRUN error bit in

the status register, abort the transmission and wait in the data state for a stop command.

• Block read

The basic unit of data transfer is a block whose maximum size is defined in the CSD (READ_BLK_LEN).

READ_BLK_PARTIAL is set, thus smaller blocks whose starting and ending address are wholly contained

within one physical block (as defined by READ_BLK_LEN) may also be transmitted. A 16-bit CRC is

appended to the end of each block ensuring data transfer integrity. READ_SINGLE_BLOCK (CMD17)

starts a block read and after a complete transfer the card goes back to Transfer State.

READ_MULTIPLE_BLOCK (CMD18) starts a transfer of several consecutive blocks. Two types of

multiple block read transactions are defined (the host can use either one at any time):

• Open-ended Multiple block read

The number of blocks for the read multiple block operation is not defined. The card will

continuously transfer data blocks until a stop transmission command is received.

• Multiple block read with pre-defined block count

The card will transfer the requested number of data blocks, terminate the transaction and return to

transfer state. Stop command is not required at the end of this type of multiple block read, unless

terminated with an error. In order to start a multiple block read with pre-defined block count, the

host must use the SET_BLOCK_COUNT command (CMD23) immediately preceding the

READ_MULTIPLE_BLOCK (CMD18) command. Otherwise the card will start an open-ended

multiple block read which can be stopped using the STOP_TRANSMISSION command.

The host can abort reading at any time, within a multiple block operation, regardless of the its type.

Transaction abort is done by sending the stop transmission command.

If the card detects an error (e.g. out of range, address misalignment, internal error, etc.) during a multiple

block read operation (both types) it will stop data transmission and remain in the Data State. The host must

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