H8S2339 Datasheet, PDF (310/1244 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series

Section 7 DMA Controller
resumes after the end of the single cycle, DREQ pin low level sampling is performed again, and
this operation is repeated until the transfer ends.
DREQ Pin Low Level Activation Timing: Set the DTA bit for the channel for which the DREQ
pin is selected to 1.
Figure 7.32 shows an example of DREQ pin low level activated single address mode transfer.
φ
DREQ
Bus release
DMA single Bus release
DMA single
Bus
release
Address bus
DACK
Transfer source/
destination
Transfer source/
destination
DMA control Idle
Single
Idle
Single
Idle
Channel
Request
Minimum of
2 cycles
Request clear
period
Request
Minimum of
2 cycles
Request clear
period
[1]
[2]
[3]
[4]
[5]
[6]
[7]
Acceptance resumes
Acceptance resumes
[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] The DMAC cycle is started.
[4] [7] Acceptance is resumed after the single 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 7.32 Example of DREQ Pin Low Level Activated Single Address Mode Transfer
DREQ pin sampling is performed every cycle, with the rising edge of the next φ cycle after the
end of the DMABCR write cycle for setting the transfer enabled state as the starting point.
Rev.4.00 Sep. 07, 2007 Page 280 of 1210
REJ09B0245-0400