Value
Content
Bits
0x0D
Register address
25:9
-
Don't care
8
Function number that is to be
resumed
Write data
7:0
5. Write the block size value to the
blksiz
register. Data is transferred in units of this block size.
†
6. Write the byte count value to the
bytcnt
register. Specify the total size of the data that is the remaining
bytes to be transferred. It is the responsibility of the software to handle the data.
†
To determine the number of pending bytes to transfer, read the transferred CIU card byte count register
(
tcbcnt
). Subtract this value from the total transfer size to calculate the number of remaining bytes to
transfer.
†
7. Write to the
cmd
register similar to a block transfer operation. When the
cmd
register is written, the
command is sent and the function resumes data transfer. For more information, refer to
Single-Block or
Multiple-Block Read
and
Single-Block or Multiple-Block Write
.
†
8. Read the resume data flag (DF) of the SDIO card device. Interpret the DF flag as follows:
†
• DF=1—The function has data for the transfer and begins a data transfer as soon as the function or
memory is resumed.
†
• DF=0—The function has no data for the transfer. If the data transfer is a read, the controller waits for
data. After the data timeout period, it issues a data timeout error.
†
Related Information
•
To learn more about how SD technology works, visit the SD Association website.
•
Single-Block or Multiple-Block Read
on page 11-38
Refer to this section for more information about writing to the
cmd
register.
•
Single-Block or Multiple-Block Write
on page 11-41
Refer to this section for more information about writing to the
cmd
register.
Read-Wait Sequence
Read_wait is used with SDIO cards only. It temporarily stalls the data transfer, either from functions or
memory, and allows the host to send commands to any function within the SDIO card device. The host can
stall this transfer for as long as required. The controller provides the facility to signal this stall transfer to the
card.
†
Signalling a Stall
To signal the stall, perform the following steps:
†
1. Check if the card supports the read_wait facility by reading the SDIO card’s SRW bit, bit 2 at offset 0x8
in the CCCR.
†
2. If this bit is 1, all functions in the card support the read_wait facility. Use the SD/SDIO IO_RW_DIRECT
command to read this bit.
†
Altera Corporation
SD/MMC Controller
11-49
Read-Wait Sequence
cv_54011
2013.12.30