Datasheet

Section 7 DMA Controller (DMAC)
Page 376 of 1384 R01UH0310EJ0500 Rev. 5.00
Sep 25, 2012
H8S/2426, H8S/2426R, H8S/2424 Group
(3) Full Address Mode (Burst Mode)
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.
DMA
read
Address bus
φ
RD
LWR
TEND
HWR
Bus release
DMA
write
DMA
dead
DMA
read
DMA
write
DMA
read
DMA
write
Bus release
Burst transfer
Last transfer cycle
Figure 7.20 Example of Full Address Mode Transfer (Burst Mode)
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.