SH7750_08 Datasheet, PDF (737/1162 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

Section 14 Direct Memory Access Controller (DMAC)
7. When falling edge detection is used for external requests, keep the external request pin high
when making DMAC settings.
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.)
10. SH7750 Only: When a DMA transfer is performed between an on-chip peripheral module and
external memory, the data may not be transferred correctly if the following conditions apply.
To work around this problem, use the CPU to transfer the data.
⎯ Conditions Under which Problem Occurs
a. Big endian is selected.
b. The external memory bus width is 32 bits.
c. Data is being transferred from an on-chip peripheral module*¹ to external memory.
d. The transmit size*² of the data to be transferred is 32 bits.
Conditions a. to d. must all be satisfied.
⎯ Description of Problem
When transferring data from an on-chip peripheral module, bits 15 to 8 of the 32-bit data
become misaligned. As a result, the data is not transferred correctly.
Data that should be transferred:
12 34 56 78
Data actually transferred to external memory: 12 34 12 78
Notes: 1. The registers corresponding to the above conditions are the following.
TMU.TCOR0
TMU.TCNT0
TMU.TCOR1
TMU.TCNT1
TMU.TCOR2
TMU.TCNT2
TMU.TCPR2
H-UDI.SDDR
2. Set by the transmit size bits in the DMA channel control register.
Rev.7.00 Oct. 10, 2008 Page 653 of 1074
REJ09B0366-0700