Hitachi SH7750 Hardware Manual page 642

8. When using the DMAC in single address mode, set an external address as the address. All
channels will halt due to an address error if an on-chip peripheral module address is set.
9. In external request (DREQ) edge detection in the SH7750R, an external request that has been
accepted can be cancelled in the following way. Firstly, negate DREQ and change the value of
CHCR.DS from 1 to 0. After that, set the CHCR.DS bit back to 1, then assert DREQ. (Though
the SH7750R does not have a DMAOR.COD bit, similar to when the DMAOR.COD bit is 1 in
the SH7750S, external requests that have once been accepted can be cancelled when the
external request (DREQ) edge is detected.)
Rev. 6.0, 07/02, page 592 of 986