r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 407

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

(4)
Set the DTA bit in DMABCRH to 1 for the channel for which the DREQ pin is selected.
Figure 7.31 shows an example of single address mode transfer activated by the DREQ pin low
level.
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.
Figure 7.31 Example of DREQ Pin Low Level Activated Single Address Mode Transfer
Address bus
DMA control
[1]
[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.
Note: In write data buffer mode, bus breaks from [2] to [7] may be hidden, and not visible.
DREQ Pin Low Level Activation Timing
Channel
DREQ
DACK
Acceptance after transfer enabling; the DREQ pin low level is sampled on the rising edge of φ,
and the request is held.
(As in [1], the DREQ pin low level is sampled on the rising edge of φ, and the request is held.)
φ
Idle
[1]
Request
Bus release
Minimum of
2 cycles
[2]
[3]
Single
Request clear
Transfer source/
DMA single
destination
period
Acceptance resumes
Idle
[4]
Request
Bus release
Minimum of
Rev. 1.00 Sep. 19, 2008 Page 379 of 1270
2 cycles
[5]
Section 7 DMA Controller (DMAC)
[6]
Single
Request clear
DMA single
Transfer source/
period
destination
Acceptance resumes
Idle
REJ09B0466-0100
[7]
release
Bus