H8S2426 Datasheet, PDF (444/1302 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8S Family / H8S/2400 Series

Section 8 EXDMA Controller (EXDMAC)
8.4.5 Transfer Modes
There are two transfer modes: normal transfer mode and block transfer mode. When the activation
source is an external request, either normal transfer mode or block transfer mode can be selected.
When the activation source is an auto request, normal transfer mode is used.
(1) Normal Transfer Mode
In normal transfer mode, transfer of one transfer unit is processed in response to one transfer
request. EDTCR functions as a 24-bit transfer counter.
The ETEND signal is output only for the last DMA transfer. The EDRAK signal is output each
time a transfer request is accepted and transfer processing is started.
Figure 8.7 shows examples of DMA transfer timing in normal transfer mode.
EXDMA
transfer cycle
Bus cycle
ETEND
Read Write
Transfer conditions:
Dual address mode, auto request mode
Last EXDMA
transfer cycle
Read Write
EDREQ
EDRAK
Bus cycle
EXDMA
EXDMA
EDACK
Transfer conditions:
Single address mode, external request mode
Figure 8.7 Examples of Timing in Normal Transfer Mode
Rev. 1.00 Sep. 19, 2008 Page 416 of 1270
REJ09B0466-0100