SDMA Channels and IDMA Emulation
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
19-7
19.3.2
IDMA Parameter RAM
Both IDMA channels have a dedicated portion of dual-port RAM for channel parameters.
Table 19-4
shows the memory map.
19.3.3
IDMA Registers
Each IDMA channel has a DMA channel mode register (DCMR), an IDMA status register (IDSR) and
corresponding mask register (IDMR) that contain global channel parameters.
Table 19-4. IDMA Parameter RAM Memory Map
Offset
1
1
IDMA1 base = IMMR + 0x3CC0
IDMA2 base = IMMR + 0x3DC0
Name
Width
Description
0x00
IBASE
Hword
IDMA BD base address. Defines the base address of the area in dual-port RAM
set aside for this channel’s BD table. It is an offset from the beginning of dual-port
RAM. Note that IBASE should be burst-aligned (divisible by 16).
0x02
DCMR
Hword
DMA channel mode register. See
Section 19.3.3.1, “DMA Channel Mode
Registers (DCMR).”
0x04
SAPR
Word
Source data pointer (internal-use). Points to the next source byte to be read.The
CP initializes SAPR to the BD’s source buffer pointer and increments it
automatically if the source is memory (DCMR[S/D] = 0bx0).
0x08
DAPR
Word
Destination data pointer (internal-use). Points to the next destination byte to be
written. The CP initializes DAPR to the BD’s destination buffer pointer, and
increments it automatically if the destination is memory (DCMR[S/D] = 0b0x).
0x0C
IBPTR
Hword
Current IDMA BD pointer. If the IDMA channel is idle, IBPTR points to the next
valid BD in the table. After a reset, or when the end (wrap bit) of the BD table is
reached, the CP wraps IBPTR back to IBASE.
0x0E
WRITE_SP
Hword
Internal-use
0x10
S_BYTE_C
Word
Internal source byte count
0x14
D_BYTE_C
Word
Internal destination byte count
0x18
S_STATE
Word
Internal state
0x1C
ITEMP
4 Words Temp data storage
0x2C
SR_MEM
Word
Data storage for peripheral write
0x30
READ_SP
Hword
Internal-use
0x32
—
Hword
Difference between source and destination residue
0x34
—
Hword
Temp storage address pointer
0x36
—
Hword
SR_MEM byte count
0x38
D_STATE
Word
Reserved. Internal state used by CP
Note:
Boldfaced items must be initialized by the user before enabling an IDMA channel. The remaining parameters
are used by the CP only.
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