r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 396

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

Section 7 DMA Controller (DMAC)
(3)
Figure 7.20 shows a transfer example in which TEND output is enabled and word-size full address
mode transfer (burst mode) is performed from external 16-bit, 2-state access space to external 16-
bit, 2-state access space.
In burst mode, one-byte or one-word transfers are executed consecutively until transfer ends.
In the transfer end cycle (the cycle in which the transfer counter reaches 0), a one-state DMA dead
cycle is inserted after the DMA write cycle.
If a request from another higher-priority channel is generated after burst transfer starts, that
channel has to wait until the burst transfer ends.
If an NMI interrupt is generated while a channel designated for burst transfer is in the transfer
enabled state, the DTME bit in DMABCRL is cleared and the channel is placed in the transfer
disabled state. If burst transfer has already been activated inside the DMAC, the bus is released on
completion of a one-byte or one-word transfer within the burst transfer, and burst transfer is
suspended. If the last transfer cycle of the burst transfer has already been activated inside the
DMAC, execution continues to the end of the transfer even if the DTME bit is cleared.
Rev. 1.00 Sep. 19, 2008 Page 368 of 1270
REJ09B0466-0100
Address bus
Full Address Mode (Burst Mode)
TEND
HWR
Bus release
LWR
RD
φ
Figure 7.20 Example of Full Address Mode Transfer (Burst Mode)
DMA
read
DMA
write
DMA
read
Burst transfer
DMA
write
DMA
read
Last transfer cycle
DMA
write
DMA
dead
Bus release