Datasheet

Section 7 DMA Controller (DMAC)
Page 380 of 1384 R01UH0310EJ0500 Rev. 5.00
Sep 25, 2012
H8S/2426, H8S/2426R, H8S/2424 Group
Figure 7.23 shows an example of block transfer mode transfer activated by the DREQ pin falling
edge.
DMA
read
Address
bus
φ
DREQ
Idle Write
Bus release
DMA
control
Channel
Write
Transfer source
Request
[1] [3][2] [4] [6][5] [7]
Acceptance resumes
DMA
dead
1 block transfer
IdleDead Dead
DMA
write
Bus
release
DMA
read
DMA
write
DMA
dead
Bus
release
Transfer source
Request
Acceptance resumes
1 block transfer
Transfer destinationTransfer destination
ReadIdleRead
Minimum
of 2 cycles
Minimum
of 2 cycles
Request clear periodRequest clear period
[1] Acceptance after transfer enabling; the DREQ pin low level is sampled on the rising edge of φ,
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; DREQ pin high level sampling on the rising edge of φ starts.
[4] [7] When the DREQ pin high level has been sampled, acceptance is resumed after the dead cycle
is completed.
(As in [1], the DREQ pin low level is sampled on the rising edge of φ, and the request is held.)
Note: In write data buffer mode, bus breaks from [2] to [7] may be hidden, and not visible.
Figure 7.23 Example of DREQ Pin Falling Edge Activated Block Transfer Mode Transfer