Rev. 1.0, 09/01, page 297 of 904
DMA
read
ø
Address
bus
Idle
Write
Idle
Bus release
DMA
control
Channel
Write
Idle
Transfer source
Request
[1]
[3]
[2]
[4]
[6]
[5]
[7]
Acceptance resumes
Acceptance resumes
DMA
write
Bus
release
DMA
read
DMA
write
Bus
release
Request
Transfer destination
Transfer source
Transfer destination
Read
Read
Request clear period
Request clear period
Minimum
of 2 cycles
Minimum
of 2 cycles
[1]
Acceptance after transfer enabling; the
pin low level is sampled on the rising edge of ø,
and the request is held.
[2] [5] The request is cleared at the next bus break, and activation is started in the DMAC.
[3] [6] Start of DMA cycle;
pin high level sampling on the rising edge of ø starts.
[4] [7] When the
pin high level has been sampled, acceptance is resumed after the write cycle
is completed.
(As in [1], the
pin low level is sampled on the rising edge of ø, and the request is held.)
Note: In write data buffer mode, bus breaks from [2] to [7] may be hidden, and not visible.
Figure 7.22 Example of
'5(4
#
'5(4
#
'5(4
#
'5(4
#
Pin Falling Edge Activated Normal Mode Transfer
'5(4
pin sampling is performed every cycle, with the rising edge of the next ø cycle after the
end of the DMABCR write cycle for setting the transfer enabled state as the starting point.
When the
'5(4
pin low level is sampled while acceptance by means of the
'5(4
pin is
possible, the request is held in the DMAC. Then, when activation is initiated in the DMAC, the
request is cleared, and
'5(4
pin high level sampling for edge detection is started. If
'5(4
pin
high level sampling has been completed by the time the DMA write cycle ends, acceptance
resumes after the end of the write cycle,
'5(4
pin low level sampling is performed again, and
this operation is repeated until the transfer ends.
Figure 7.23 shows an example of block transfer mode transfer activated by the
'5(4
pin falling
edge.
Содержание H8S/2376 F-ZTAT
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