MAX32665-MAX32668 User Guide
Maxim Integrated Page 198 of 457
Block Gap Control Register
Read Wait Control
If the card supports read wait (optional for SDIO cards), setting this bit enables
use of the read wait protocol to stop reading data using the SDHC_DAT[2] line. If
the card does not support read wait, the SDHC stops the SD Clock to hold read
data, preventing command generation. When a card is inserted, the card driver
must set this field based on the CCCR of the SDIO card inserted.
Suspend/Resume is not supported when this bit is set to 0.
1: Enable Read Wait Control
0: Disable Read Wait Control
Note: If the SDIO card does not support read wait, then you must not set this bit to
1. Setting it to 1 when read wait is not supported might cause a SDHC_DAT line
conflict.
Continue Request
This bit is used to restart a transaction that was stopped using the Stop At Block
Gap Request (SDHC_BLK_GAP.stop). To cancel a stop at the block gap, set
SDHC_BLK_GAP.stop to 0, and set this bit, SDHC_BLK_GAP.cont, to 1 to restart
the transfer.
This bit is automatically cleared by hardware for either of the following
conditions:
• During a read transaction, the DAT Line Active changes from 0 to 1 as the
write transaction restarts.
• During a write transaction, the Write Transfer Active changes from 0 to 1 as
the write transaction restarts.
1: Restart
0: No effect
Stop At Block Gap Request
Setting this bit stops executing read and write transactions at the next block gap
for non-DMA, SDMA, and ADMA transfers. This bit must remain set to 1 until the
SDHC_INT_STAT.trans_comp bit is set to 1.
For write transfers where the card driver writes data to the Buffer Data Port
Register (SDHC_BUFFER), the card driver must set this bit after all block data is
written.
1: Stop
0: Transfer
This bit affects the following fields:
• Read Transfer Active, SDHC_PRESENT.read_transfer
• Write Transfer Active, SDHC_PRESENT.write_transfer
• SDHC_DAT Line Active, SDHC_PRESENT.dat_line_active
• Command Inhibit (DAT), SDHC_PRESENT.dat
Note: If this bit is set to 1, the card driver must not write data to the Buffer Data
Port Register (SDHC_BUFFER).
Note: Clearing both the SDHC_BLK_GAP.stop and SDHC_BLK_GAP.cont fields does
not cause a transaction to restart.
Note: You can set this bit to 1 regardless of whether the card inserted supports
Read Wait Control. The SDHC stops the card through Read Wait Control or by
stopping the SD clock.
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