SH7706 Datasheet, PDF (315/749 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family/SH7700 Series

Section 9 Direct Memory Access Controller (DMAC)
9.4.2 DMA Transfer Requests
DMA transfer requests are basically generated in either the data transfer source or destination, but
they can also be generated by external devices and on-chip peripheral modules that are neither the
source nor the destination. Transfers can be requested in three modes: auto request, external
request, and on-chip peripheral module request. The request mode is selected in the RS3 to RS0
bits of CHCR_0 to CHCR_3.
Auto-Request Mode: When there is no transfer request signal from an external source, as in a
memory-to-memory transfer or a transfer between memory and an on-chip peripheral module
unable to request a transfer, the auto-request mode allows the DMAC to automatically generate a
transfer request signal internally. When the DE bits of CHCR_0 to CHCR_3 and the DME bit of
the DMAOR are set to 1, the transfer begins so long as the TE bits of CHCR_0 to CHCR_3 and
the AE but and NMIF bit of DMAOR are all 0.
External Request Mode: In this mode a transfer is performed at the request signal (DREQ) of an
external device. Choose one of the modes shown in table 9.2 according to the application system.
When this mode is selected, if the DMA transfer is enabled (DE = 1, DME = 1, TE = 0, AE = 0,
NMIF = 0), a transfer is performed upon a request at the DREQ input. Choose to detect DREQ by
either the falling edge or low level of the signal input with the DS bit of CHCR_0 to CHCR_1 (DS
= 0 is level detection, DS = 1 is edge detection). The source of the transfer request does not have
to be the data transfer source or destination.
Table 9.2 Selecting External Request Modes with the RS Bits
RS3
0
Note:
RS2 RS1 RS0 Address Mode Source
Destination
0
0
0
Dual address Any*
mode
Any*
1
0
Single address External memory, External device with
mode
memory-mapped DACK
external device
1
External device with External memory,
DACK
memory-mapped
external device
* External memory, memory-mapped external device, on-chip memory, on-chip
peripheral module (excluding DMAC, UBC, and BSC)
Rev. 5.00 May 29, 2006 page 267 of 698
REJ09B0146-0500