100分发问：SDIO Response R4 的结构说明（CMD5的回应）

SDIO 不用ACMD41，换成了CMD5，Response也变了！

[编辑 -  2/1/05 by  zmwk]

 做过的朋友帮帮忙啊！

Come on!

N年前的贴了，不知道还在看没

An SDIO card receiving CMD5 shall respond with a SDIO unique response, R4. The format of R4 for both the
SD and SPI modes is:
S D Reserved C Number
of I/O
functions
Memory
Present
Stuff
Bits
I/O OCR Reserved E
1 1 6 1 3 1 3 24 7 1
Figure 3-5 Response R4 in SD mode
Modified
R1
C Number
of I/O
functions
Memory
Present
Stuff Bits I/O OCR
8 1 3 1 3 24
Figure 3-6 Response R4 in SPI mode
The Response, R4 contains the following data:
S(tart bit): Start bit. Always 0
D(irection): Direction. Always 0. Indicates transfer from card to host.
Reserved: Bits reserved for future use. These bits shall be set to 1.
C: Set to 1 if Card is ready to operate after initialization
I/O OCR: Operation Conditions Register. The supported minimum and maximum values
for VDD. The layout of the OCR is shown in Table 3-1. See section 4.9.1 for
additional information.
Memory Present: Set to 1 if the card also contains SD memory. Set to 0 if the card is I/O only.
Number of I/O Functions: Indicates the total number of I/O functions supported by this card. The range is 0-7.
Note that the common area present on all I/O cards at Function 0 is not included in
this count. The I/O functions shall be implemented sequentially beginning at
function 1.
Modified R1: The SPI R1 response byte as described in Figure 47 of the SD Physical
Specification Version 1.01 modified for I/O as follows:
Figure 3-7 Modified R1 Response
Stuff Bits: Not used, shall be set to 0.
1 = in idle state
RFU (always 0)
1 = illegal command
1 = COM CRC error
1 = Function number error
RFU (always 0)
1 = parameter error
Start Bit (always 0)
0 0 0
?Copyright 2001-2006 SD Card Association
SDIO Simplified Specification Version 1.10
11
Once an SDIO card has received a CMD5, the I/O portion of that card is enabled to respond normally to all
further commands. This I/O enable of the functions within the I/O card shall remain set until a reset, power
cycle or CMD52 with write to I/O reset is received by the card. Note that a SD memory only card may respond
to a CMD5. The proper response for a memory only card would be Memory Present = 1 and Number of I/O
Functions = 0. A memory only card built to SD Memory Card specification version 1.01 would detect the CMD5
as an illegal command and not respond. Note that unlike the similar memory command ACMD41, The SPI
response to CMD5 does contain the OCR value from the card.
The I/O aware host sends CMD5. If the card responds with response R4 within the timeout value of Ncr as
defined in the SD Physical Specification Version 1.01, the host determines the card's configuration based on
the data contained within the R4.

去看下手册就有了呗