r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 469

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

(4)
Figure 8.27 shows an example of single address mode transfer activated by the EDREQ pin low
level.
EDREQ pin sampling is performed in each cycle starting at the next rise of φ after the end of the
EDMDR write cycle for setting the transfer-enabled state.
When a low level is sampled at the EDREQ pin while acceptance via the EDREQ pin is possible,
the request is held within the EXDMAC. Then when activation is initiated within the EXDMAC,
the request is cleared. At the end of the single cycle, acceptance resumes and EDREQ pin low
level sampling is performed again; this sequence of operations is repeated until the end of the
transfer.
Figure 8.27 Example of Single Address Mode Transfer Activated by EDREQ Pin Low Level
[1]
[2], [5] Request is cleared at end of next bus cycle, and activation is started in EXDMAC.
[3], [6] DMA cycle is started.
[4], [7] Acceptance is resumed after completion of single cycle.
EDREQ Pin Low Level Activation Timing
Acceptance after transfer enabling; EDREQ pin low level is sampled at rise of φ, and request is held.
(As in [1], EDREQ pin low level is sampled at rise of φ, and request is held.)
φ
EDREQ
Address bus
EDACK
DMA control
Channel
Idle
[1]
Minimum 3 cycles
Request
Bus release
[2]
clearance period
Single
[3]
Request
DMA single
Transfer source/
destination
Idle
Acceptance
resumed
[4]
Minimum 3 cycles
Request
Bus release
[5]
Rev. 1.00 Sep. 19, 2008 Page 439 of 1342
clearance period
Section 8 EXDMA Controller (EXDMAC)
Single
[6]
Request
DMA single Bus release
Transfer source/
destination
Idle
Acceptance
resumed
[7]
REJ09B0467-0100