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ATSAM4S-XPLD
817
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
Note:
1. If the command is SEND_OP_COND, the CRC error flag is always present (refer to R3 response in the High Speed
MultiMedia Card specification).
37.8.2 Data Transfer Operation
The High Speed MultiMedia Card allows several read/write operations (single block, multiple blocks, stream, etc.). These
kinds of transfer can be selected setting the Transfer Type (TRTYP) field in the HSMCI Command Register
(HSMCI_CMDR).
kinds of transfer can be selected setting the Transfer Type (TRTYP) field in the HSMCI Command Register
(HSMCI_CMDR).
These operations can be done using the features of the Peripheral DMA Controller (PDC). If the PDCMODE bit is set in
HSMCI_MR, then all reads and writes use the PDC facilities.
HSMCI_MR, then all reads and writes use the PDC facilities.
In all cases, the block length (BLKLEN field) must be defined either in the Mode Register HSMCI_MR, or in the Block
Register HSMCI_BLKR. This field determines the size of the data block.
Register HSMCI_BLKR. This field determines the size of the data block.
Consequent to MMC Specification 3.1, two types of multiple block read (or write) transactions are defined (the host can
use either one at any time):
use either one at any time):
Open-ended/Infinite Multiple block read (or write):
The number of blocks for the read (or write) multiple block operation is not defined. The card will continuously
transfer (or program) data blocks until a stop transmission command is received.
transfer (or program) data blocks until a stop transmission command is received.
Multiple block read (or write) with pre-defined block count (since version 3.1 and higher):
The card will transfer (or program) the requested number of data blocks and terminate the transaction. The stop
command is not required at the end of this type of multiple block read (or write), unless terminated with an error. In
order to start a multiple block read (or write) with pre-defined block count, the host must correctly program the
HSMCI Block Register (HSMCI_BLKR). Otherwise the card will start an open-ended multiple block read. The
BCNT field of the Block Register defines the number of blocks to transfer (from 1 to 65535 blocks). Programming
the value 0 in the BCNT field corresponds to an infinite block transfer.
command is not required at the end of this type of multiple block read (or write), unless terminated with an error. In
order to start a multiple block read (or write) with pre-defined block count, the host must correctly program the
HSMCI Block Register (HSMCI_BLKR). Otherwise the card will start an open-ended multiple block read. The
BCNT field of the Block Register defines the number of blocks to transfer (from 1 to 65535 blocks). Programming
the value 0 in the BCNT field corresponds to an infinite block transfer.
37.8.3 Read Operation
The following flowchart shows how to read a single block with or without use of PDC facilities. In this example (see
), a polling method is used to wait for the end of read. Similarly, the user can configure the Interrupt Enable Register
(HSMCI_IER) to trigger an interrupt at the end of read.