Datasheet

674
SAM9M10 [DATASHEET]
6355F–ATARM–12-Mar-13
35.8.1 Command - Response Operation
After reset, the HSMCI is disabled and becomes valid after setting the MCIEN bit in the HSMCI_CR Control
Register.
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.
All the timings for High Speed MultiMedia Card are defined in the High Speed MultiMediaCard System
Specification.
The two bus modes (open drain and push/pull) needed to process all the operations are defined in the HSMCI
command register. The HSMCI_CMDR allows a command to be carried out.
For example, to perform an ALL_SEND_CID command:
The command ALL_SEND_CID and the fields and values for the HSMCI_CMDR Control Register are described in
Table 35-6 and Table 35-7.
Note: bcr means broadcast command with response.
The HSMCI_ARGR contains the argument field of the command.
To send a command, the user must perform the following steps:
• Fill the argument register (HSMCI_ARGR) with the command argument.
• Set the command register (HSMCI_CMDR) (see Table 35-7).
The command is sent immediately after writing the command register.
Host Command N
ID
Cycles CID
CMD S T Content CRC E Z ****** Z S T Content Z Z Z
Table 35-6. ALL_SEND_CID Command Description
CMD Index Type Argument Resp Abbreviation
Command
Description
CMD2 bcr [31:0] stuff bits R2 ALL_SEND_CID
Asks all cards to send
their CID numbers on
the CMD line
Table 35-7. Fields and Values for HSMCI_CMDR Command Register
Field Value
CMDNB (command number) 2 (CMD2)
RSPTYP (response type) 2 (R2: 136 bits response)
SPCMD (special command) 0 (not a special command)
OPCMD (open drain command) 1
MAXLAT (max latency for command to response) 0 (NID cycles ==> 5 cycles)
TRCMD (transfer command) 0 (No transfer)
TRDIR (transfer direction) X (available only in transfer command)
TRTYP (transfer type) X (available only in transfer command)
IOSPCMD (SDIO special command) 0 (not a special command)