MMC/SD Host Controller
7-147
MPU Public Peripherals
This register configures the number of blocks for a multiple block data transfer
(read or write) operation for MMC/SD cards. This register is not used for SPI
transfers.
Table 7–108. MMC Number of Blocks Register (MMC_NBLK)
Bit
Name
Description
15–11
Reserved
10 – 0
NBLK
Number of blocks value
Number of Blocks (NBLK)
MMC/SD mode only.
In MMC/SD mode, this 11-bit value (bits 10-0) specifies the number of blocks
for a multiple block data transfer (read or write). Each block is of size
MMC_BLEN:BLEN (block length value). This value must be set with the num-
ber of blocks – 1.
This register must be programmed prior to any multiple block data transfer. A
write into this register initializes an 11-bit counter that decrements by one after
each block transfer. A read into this register returns the number of blocks
remaining to be transferred to the card.
When the counter reaches 0, the transfer stops after the last transfer
completes.
For stream or multiple block transfer, a Block_RS interrupt is generated only
once after the last successful transfer when NBLK reaches 0.
In stream mode, the minimum allowable number of blocks is two blocks.
Note:
This value must be 0x000 for a single block transfer. In stream mode, the
minimum allowable number of blocks is two blocks. If the transfer is inter-
rupted by a STOP_TRANSMISSION command (CMD12) before the counter
reached 0, you must reprogram this register prior to starting any new single
or multiple block data transfers.
-
0x000: 1 block
-
0x7FF: 2048 blocks
Values after reset are low (all 11 bits).