HD6417706 RENESAS [Renesas Technology Corp], HD6417706 Datasheet - Page 303

• Manufacturer Part Number: HD6417706
• Description: Renesas 32-Bit RISC Microcomputer Super RISC engine Family/SH7700 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

9.4.2
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
Note:
RS3
0
* External memory, memory-mapped external device, on-chip memory, on-chip
RS2
0
DMA Transfer Requests
peripheral module (excluding DMAC, UBC, and BSC)
Selecting External Request Modes with the RS Bits
RS1
0
1
RS0
0
0
1
Address Mode
Dual address
mode
Single address
mode
Source
Any*
External memory,
memory-mapped
external device
External device with
DACK
Rev. 4.00, 03/04, page 257 of 660
Destination
Any*
External device with
DACK
External memory,
memory-mapped
external device