Renesas SH7781 - Manual (Page 1208)

24. Multimedia Card Interface (MMCIF)
Rev.1.00 Jan. 10, 2008 Page 1178 of 1658
REJ09B0261-0100
(2) CMDR5
Bit:
Initial value:
R/W:
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
R
CRC End
R R R R R R R
Bit Bit Name
Initial
Value R/W Description
7 to 1 CRC All 0 R These bits are always read as 0. The write value should
always be 0.
0 End 0 R This bit is always read as 0. The write value should
always be 0.
24.3.2 Command Start Register (CMDSTRT)
CMDSTRT is an 8-bit readable/writable register that triggers the start of command transmission,
representing the start of a command sequence. The following operations should have been
completed before the command sequence starts.
• Analysis of prior command response, clearing the command response register write if
necessary
• Analysis/transfer of receive data of prior command if necessary
• Preparation of transmit data of the next command if necessary
• Setting of CMDTYR, RSPTYR, TBCR and TBNCR
• Setting of CMDR0 to CMDR4
The CMDR0 to CMDR4, CMDTYR, RSPTYR, TBCR and TBNCR registers should not be
changed until command transmission has ended (during the CWRE flag in CSTR has been set
to 1 or until command transmit end interrupt has occurred).
Command sequences are controlled by the sequencers in both the MMCIF side and the MMC card
side. Normally, these operate synchronously. However, if an error occurs or a command is
aborted, these may become temporarily unsynchronized. Be careful when setting the CMDOFF bit
in OPCR, issuing the CMD12 command, or processing an error in MMC mode. A new command
sequence should be started only after the end of the command sequence on both the MMCIF and
card sides is confirmed. See section24.4, Operation when an error occurred.