UM10503
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User manual
Rev. 1.3 — 6 July 2012
434 of 1269
NXP Semiconductors
UM10503
Chapter 20: LPC43xx SD/MMC interface
20.6.27 Bus Mode Register (BMOD)
20.6.28 Poll Demand Register (PLDMND)
Table 323. Bus Mode Register (BMOD, address 0x4000 4080) bit description
Bit
Symbol
Value
Description
Reset
value
0
SWR
Software Reset. When set, the DMA Controller resets all its internal registers. SWR
is read/write. It is automatically cleared after 1 clock cycle.
0
1
FB
Fixed Burst. Controls whether the AHB Master interface performs fixed burst
transfers or not. When set, the AHB will use only SINGLE, INCR4, INCR8 or
INCR16 during start of normal burst transfers. When reset, the AHB will use
SINGLE and INCR burst transfer operations. FB is read/write.
0
6:2
DSL
Descriptor Skip Length. Specifies the number of HWord/Word/Dword to skip
between two unchained descriptors. This is applicable only for dual buffer
structure. DSL is read/write.
0
7
DE
SD/MMC DMA Enable. When set, the SD/MMC DMA is enabled. DE is read/write.
10:8
PBL
Programmable Burst Length. These bits indicate the maximum number of beats to
be performed in one SD/MMC DMA transaction. The SD/MMC DMA will always
attempt to burst as specified in PBL each time it starts a Burst transfer on the host
bus. The permissible values are 1, 4, 8, 16, 32, 64, 128 and 256. This value is the
mirror of MSIZE of FIFOTH register. In order to change this value, write the
required value to FIFOTH register. This is an encode value as follows.Transfer unit
is 32 bit. PBL is a read-only value.
0
0x0
1 transfer
0x1
4 transfers
0x2
8 transfers
0x3
16 transfers
0x4
32 transfers
0x5
64 transfers
0x6
128 transfers
0x7
256 transfers
31:11
-
Reserved
Table 324. Poll Demand Register (PLDMND, address 0x4000 4084) bit description
Bit
Symbol
Description
Reset
value
31:0
PD
Poll Demand. If the OWN bit of a descriptor is not set, the FSM
goes to the Suspend state. The host needs to write any value
into this register for the SD/MMC DMA state machine to resume
normal descriptor fetch operation. This is a write only register.
PD bit is write-only.