HD64F7144F50V Datasheet, PDF (228/932 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

10. Direct Memory Access Controller (DMAC)
10.4.2 DMA Transfer Requests
DMA transfer requests are usually generated in either the data transfer source or destination, but
they can also be generated by 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 the
DMA channel control registers_0 to 3 (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 NMIF and AE bits 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 10.2 according to the application system.
When this mode is selected, if the DMA transfer is enabled (DE = 1, DME = 1, TE = 0, NMIF = 0,
AE = 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_3 (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 10.2 Selecting External Request Modes with RS Bits
RS3 RS2 RS1 RS0 Address Mode Source
Destination
0
0
0
0
Dual address Any*
mode
Any*
0
0
1
0
Single address External memory or External device with
mode
memory-mapped DACK
external device
0
0
1
1
Single address External device with External memory or
mode
DACK
memory-mapped
external device
Note: * External memory, memory-mapped external device, on-chip memory, and on-chip
peripheral module (excluding DMAC, DTC, BSC, UBC).
Rev.4.00 Mar. 27, 2008 Page 182 of 882
REJ09B0108-0400