SH7144 Datasheet, PDF (230/773 Pages) Renesas Technology Corp – Hitachi SuperH RISC engine

10.6 Cautions on Use
1. The DMA operation register (DMAOR) can be accessed only in word (16-bit) units. The other
registers can be accessed in word (16-bit) or longword (32-bit) units.
2. When rewriting the RS0 to RS3 bits of CHCR0 to CHCR3, first clear the DE bit to 0 (set the
DE bit to 0 before doing rewrites with CHCR).
3. When an NMI interrupt is input, the NMIF bit of the DMAOR is set even when the DMAC is
not operating.
4. Set the DME bit of the DMAOR to 0 and make certain that any DMAC received transfer
request processing has been completed before entering standby mode.
5. Do not access the DMAC, DTC, BSC, or UBC on-chip peripheral modules from the DMAC.
6. When activating the DMAC, do the CHCR or DMAOR setting as the final step. There are
instances where abnormal operation will result if any other registers are established last.
7. After the DMATCR count becomes 0 and the DMA transfer ends normally, always write a 0 to
the DMATCR, even when executing the maximum number of transfers on the same channel.
There are instances where abnormal operation will result if this is not done.
8. Designate burst mode as the transfer mode when using the address reload function. There are
instances where abnormal operation will result in cycle steal mode.
9. Designate a multiple of four for the DMATCR value when using the address reload function.
There are instances where abnormal operation will result if anything else is designated.
10. When detecting external requests by falling edge, maintain the external request pin at high
level when performing the DMAC establishment.
11. When operating in single address mode, establish an external address as the address. There are
instances where abnormal operation will result if an internal address is established.
12. Do not access DMAC register empty addresses (H'FFFF86B2 to H'FFFF86BF). Operation
cannot be guaranteed when empty addresses are accessed.
Rev. 2.0, 09/02, page 190 of 732