SH7080_09 Datasheet, PDF (481/1622 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family

Section 10 Direct Memory Access Controller (DMAC)
10.5 Usage Notes
10.5.1 Notes on Output from DACK Pin
When burst mode and cycle steal mode are specified in multiple channels at the same time,
unnecessary DACK may be asserted at the end of burst transfer if the following conditions are all
satisfied.
1. When DMA transfer is performed with burst mode and cycle steal mode being specified in
multiple channels at the same time.
2. When dual address mode is specified for the channel used in burst mode and DACK output is
enabled in write cycles.
3. When the DMAC cannot acquire the bus mastership after the end of burst transfer while the
DMAC has accepted a cycle-steal transfer request.
This can be avoided by one of the following actions.
Action 1: After confirming the end of burst transfer (TE bit = 1), perform remaining DMA transfer
in cycle steal mode.
Action 2: Do not enable DACK in write cycles for the channel used in burst mode.
Action 3: When performing DMA transfer in multiple channels at the same time, select either
burst mode or cycle steal mode for all channels.
10.5.2 DMA Transfer by Peripheral Modules
During DMA transfer by peripheral modules, do not set the clock ratio of bus clock
(Bφ):peripheral clock (Pφ), bus clock (Bφ):MTU2 clock (MPφ), and bus clock (Bφ):MTU2S clock
(MIφ) to 1:1/3 or 1:1/4
10.5.3 Module Standby Mode Setting
DMAC operation can be enabled or disabled by setting the standby control register. The DMAC is
disabled by default. After module standby mode is canceled, access to the DMAC registers is
enabled.
Note that software standby mode or module standby mode must not be entered while the DMAC
is operating. Before entering software standby mode or module standby mode, return the channel
control registers (CHCR_0 to CHCR_3) and DMA operation register (DMAOR) to their initial
values. For details, refer to section 26, Power-Down Modes.
Rev. 4.00 Dec. 15, 2009 Page 421 of 1558
REJ09B0181-0400