20-6
MPC860 PowerQUICC UserÕs Manual
MOTOROLA
Part V. The Communications Processor Module
(ßy-by) burst transfers. Note that single-buffering is available only on IDMA1. This mode
also remaps the IDMA1 channel parameter RAM. See Section 20.3.9, ÒSingle-Buffer
Mode on IDMA1ÑA Special Case.Ó
Note that DREQ0 is the DMA request for IDMA1, and DREQ1 is the DMA request for
IDMA2.
20.3.1 IDMA Features
The following is a list of IDMAÕs main features:
¥
Two independent, fully programmable DMA channels
¥
Dual-address or single-address transfers with 32-bit address and data capability
¥
32-bit byte transfer counters allow for 4-Gbyte buffers
¥
Byte, half-word, word, or 4-word burst quantities for transfers
¥
32-bit, byte-addressable buffer pointers auto-increment for memory accesses and
remain constant for peripheral accesses
¥
Byte-packing and unpacking algorithms use the absolute minimum number of bus
cycles required during dual-address transfers
¥
All bus-termination modes, such as TA, TEA, and BI, are supported
¥
DMA handshaking for cycle-steal and burst transfers
¥
Two buffer handling modesÑauto-buffering and buffer-chaining
¥
Optimized, low-overhead single-buffer mode for peripheral-to-memory transfers on
IDMA1
¥
The MPC860Õs chip-select and wait-state generation logic can be used with IDMA.
20.3.2 IDMA Parameter RAM
Both IDMA channels have a dedicated portion of dual-port RAM for channel parameters.
Table 20-4 shows the memory map. Note that in the special single-buffer mode, the IDMA1
parameter RAM map changes; see Section 20.3.9, ÒSingle-Buffer Mode on IDMA1ÑA
Special Case.Ó
Table 20-4. IDMA Parameter RAM Memory Map
Offset
1
Name
Width
Description
0x00
IBASE
Hword
IDMA BD base address. DeÞnes the base address of the area in dual-port RAM
set aside for this channelÕs 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 20.3.3.1, ÒDMA Channel Mode
Registers (DCMR).Ó
0x04
SAPR
Word
Source data pointer (internal-use). Points to the next source byte to be read.The
CP initializes SAPR to the BDÕs source buffer pointer and increments it
automatically if the source is memory (DCMR[S/D] = 0bx0).
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