SH7041A datasheet(275/923 Pages) RENESAS

275 / 923 page

237

A21–A0

CSn

D15–D0

DACK

WRH

WRL

Address output to external memory space

Data that is output from the external

device with DACK

DACK signal to external devices with

DACK (active low)

WR signal to external memory space

a. External device with DACK to external memory space

A21–A0

CSn

D15–D0

Address output to external memory space

Data that is output from external memory space

RD signal to external memory space

DACK signal to external device with DACK

(active low)

DACK

b. External memory space to external device with DACK

Figure 11.6 Example of DMA Transfer Timing in the Single Address Mode

11.3.6

Dual Address Mode

Dual address mode is used for access of both the transfer source and destination by address.

Transfer source and destination can be accessed either internally or externally. Dual address mode

is subdivided into two other modes: direct address transfer mode and indirect address transfer

mode.

Direct Address Transfer Mode: Data is read from the transfer source during the data read cycle,

and written to the transfer destination during the write cycle, so transfer is conducted in two bus

cycles. At this time, the transfer data is temporarily stored in the DMAC. With the kind of external

memory transfer shown in figure 11.7, data is read from one of the memories by the DMAC

during a read cycle, then written to the other external memory during the subsequent write cycle.

Figure 11.8 shows the timing for this operation.

SH7041A Scheda tecnica(PDF) 275 Page - Renesas Technology Corp