Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
1108
Command—A command is a token that starts an operation. A command is sent from the host either to a
single card (addressed command) or to all connected cards (broadcast command). A command is
transferred serially on the CMD line.
single card (addressed command) or to all connected cards (broadcast command). A command is
transferred serially on the CMD line.
Response—A response is a token which is sent from an addressed card or (synchronously) from all
connected cards to the host as an answer to a previously received command. A response is transferred
serially on the CMD line.
connected cards to the host as an answer to a previously received command. A response is transferred
serially on the CMD line.
Data—Data can be transferred from the card to the host or vice versa. Data is transferred via the data line.
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.
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 MultiMedia Card System
Specification. See also Table 41-6 on page 1109.
Specification. See also Table 41-6 on page 1109.
High Speed MultiMedia Card 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 information 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.
In addition, some operations have a data token; the others transfer their information 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:
Sequential commands—These commands initiate a continuous data stream. They are terminated only when
a stop command follows on the CMD line. This mode reduces the command overhead to an absolute
minimum.
a stop command follows on the CMD line. This mode reduces the command overhead to an absolute
minimum.
Block-oriented commands—These commands send a data block succeeded by CRC bits.
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 (see
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 (see
The HSMCI provides a set of registers to perform the entire range of High Speed MultiMedia Card operations.
41.8.1 Command - Response Operation
After reset, the HSMCI is disabled and becomes valid after setting the MCIEN bit in the HSMCI_CR.
The PWSEN bit saves power by dividing the HSMCI clock by 2
PWSDIV
+ 1 when the bus is inactive.
The two bits, RDPROOF and WRPROOF in the HSMCI Mode Register (HSMCI_MR) allow stopping the HSMCI
clock during read or write access if the internal FIFO is full. This will guarantee data integrity, not bandwidth.
clock during read or write access if the internal FIFO is full. This will guarantee data integrity, not bandwidth.
All the timings for High Speed MultiMedia Card are defined in the High Speed MultiMedia Card System
Specification.
Specification.
The two bus modes (open drain and push/pull) needed to process all the operations are defined in the HSMCI
Command Register (HSMCI_CMDR). The HSMCI_CMDR allows a command to be carried out.
Command Register (HSMCI_CMDR). The HSMCI_CMDR allows a command to be carried out.
For example, to perform an ALL_SEND_CID command:
Host Command
N
ID
Cycles
Response
High Impedance
State
CMD
S
T
Content
CRC
E
Z
******
Z
S
T
CID
Content
Z
Z
Z