UM10503
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User manual
Rev. 1.3 — 6 July 2012
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NXP Semiconductors
UM10503
Chapter 20: LPC43xx SD/MMC interface
20.7.6.1 SD/MMC DMA descriptors
20.7.6.1.1
SD/MMC DMA descriptor DESC0
The DES0 descriptor contains control and status information.
Fig 47. Chain descriptor structure
Descriptor A
Data Buffer
Descriptor C
Data Buffer
Descriptor B
Data Buffer
Table 344. SD/MMC DMA DESC0 descriptor
Bit
Symbol
Description
0
-
Reserved
1
DIC
Disable Interrupt on Completion
When set, this bit will prevent the setting of the TI/RI bit of the IDMAC Status
Register (IDSTS) for the data that ends in the buffer pointed to by this descriptor.
2
LD
Last Descriptor
When set, this bit indicates that the buffers pointed to by this descriptor are the
last buffers of the data.
3
FS
First Descriptor
When set, this bit indicates that this descriptor contains the first buffer of the
data. If the size of the first buffer is 0, next Descriptor contains the beginning of
the data.
4
CH
Second Address Chained
When set, this bit indicates that the second address in the descriptor is the Next
Descriptor address rather than the second buffer address. When this bit is set,
BS2 (DES1[25:13]) should be all zeros.
5
ER
End of Ring
When set, this bit indicates that the descriptor list reached its final descriptor.
The IDMAC returns to the base address of the list, creating a Descriptor Ring.
This is meaningful for only a dual-buffer descriptor structure.