SAM3X8E Atmel Corporation, SAM3X8E Datasheet - Page 926

• Manufacturer Part Number: SAM3X8E
• Manufacturer: Atmel Corporation

37.8
926
926
High Speed MultiMediaCard Operations
SAM3X/A
SAM3X/A
Note:
When the HSMCI is configured to operate with SD memory cards, the width of the data bus can
be selected in the HSMCI_SDCR register. Clearing the SDCBUS bit in this register means that
the width is one bit; setting it means that the width is four bits. In the case of High Speed Multi-
Media cards, only the data line 0 is used. The other data lines can be used as independent
PIOs.
After a power-on reset, the cards are initialized by a special message-based High Speed Multi-
MediaCard bus protocol. Each message is represented by one of the following tokens:
Card addressing is implemented using a session address assigned during the initialization
phase by the bus controller to all currently connected cards. Their unique CID number identifies
individual cards.
The structure of commands, responses and data blocks is described in the High Speed MultiMe-
dia-Card System Specification. See also
High Speed MultiMediaCard bus data transfers are composed of these tokens.
There are different types of operations. Addressed operations always contain a command and a
response token. In addition, some operations have a data token; the others transfer their infor-
mation directly within the command or response structure. In this case, no data token is present
in an operation. The bits on the DAT and the CMD lines are transferred synchronous to the clock
HSMCI Clock.
Two types of data transfer commands are defined:
Both read and write operations allow either single or multiple block transmission. A multiple
block transmission is terminated when a stop command follows on the CMD line similarly to the
sequential read or when a multiple block transmission has a pre-defined block count
Transfer Operation” on page
The HSMCI provides a set of registers to perform the entire range of High Speed MultiMedia
Card operations.
• Command: A command is a token that starts an operation. A command is sent from the host
• Response: A response is a token which is sent from an addressed card or (synchronously)
• Data: Data can be transferred from the card to the host or vice versa. Data is transferred via
• Sequential commands: These commands initiate a continuous data stream. They are
• Block-oriented commands: These commands send a data block succeeded by CRC bits.
either to a single card (addressed command) or to all connected cards (broadcast
command). A command is transferred serially on the CMD line.
from all connected cards to the host as an answer to a previously received command. A
response is transferred serially on the CMD line.
the data line.
terminated only when a stop command follows on the CMD line. This mode reduces the
command overhead to an absolute minimum.
When several HSMCI (x HSMCI) are embedded in a product, MCCK refers to HSMCIx_CK,
MCCDA to HSMCIx_CDA, MCDAy to HSMCIx_DAy, MCCDB to HSMCIx_CDB, MCDBy to
HSMCIx_DBy.
930.).
Table 37-6 on page
927.
11057A–ATARM–17-Feb-12
11057A–ATARM–17-Feb-12
(See “Data