20-18
MPC860 PowerQUICC UserÕs Manual
MOTOROLA
Part V. The Communications Processor Module
Figure 20-12. SDACK Timing Diagram: Single-Address
Peripheral Read, Internally-Generated TA
20.3.9 Single-Buffer Mode on IDMA1ÑA Special Case
Note that single-buffer mode is available only on MPC860 Rev. C and later.
For single-buffer transfers from a peripheral to memory of up to 64 bytes per request,
IDMA1 offers a reduced-latency solution using single-address bursts. The memory
destination address, the buffer length (byte count), and the channel mode register are stored
directly in the IDMA parameter RAM instead of in a formal BD. Table 20-9 shows the
single-buffer mode IDMA1 parameter RAM map.
Single-buffer mode is selected by setting RCCR[EIE], the CPM external interrupt enable
bit; see Section 19.5.1, ÒRISC Controller ConÞguration Register (RCCR).Ó Note that the
CPM external interrupt always refers to a special request to the CPM, not to the core.
1
From IDMA1 base = IMMR + 0x3CC0
Table 20-9. Single-Buffer Mode IDMA1 Parameter RAM Map
Offset
1
Name
Width
Description
0x00
BAPR
Word
Buffer pointer. Contains the destination buffer memory address. BAPR should be
burst-aligned. It is automatically incremented by 16 bytes after each burst.
0x04
BCR
Word
Byte count register. Contains the buffer length in bytes. BCR is decremented by 16
after each burst. BCR must be a multiple of 16. The IDMA channel will terminate the
block transfer when BCR reaches zero.
0x08
DCMR
Word
DMA channel mode register.
0x0CÐ0x3F
Ñ
Ñ
Reserved.
Note: Parameters should not be modified while DMA is active.
CLKOUT
Address
TS
R/W
Data
TA
SDACK
T3
T1
T3
T1
T3
T1
T3
T1
T3
T1
T3
T
HOLD
T
DELAY
Содержание MPC860 PowerQUICC
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