On-Demand Data Transfer Mode (Ddt Mode); Operation - Hitachi SH7750 Hardware Manual

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On-Demand Data Transfer Mode (DDT Mode)

Setting the DDT bit to 1 in DMAOR causes a transition to on-demand data transfer mode (DDT

mode). In DDT mode, it is possible to specify direct single address mode transfer to channel 0 via

the data bus and DDT module, and simultaneously issue a transfer request, using the DBREQ,

BAVL, TR, TDACK, and ID [1:0] signals between an external device and the DMAC. Figure

14.23 shows a block diagram of the DMAC, DDT, BSC, and an external device (with DBREQ,

BAVL, TR, TDACK, ID [1:0], and D [63:0] = DTR pins).

ddtmode tdack id[1:0]

Figure 14.23 On-Demand Transfer Mode Block Diagram

For channels 0 to 3, after making the settings for normal DMA transfer using the CPU, a transfer

request can be issued from an external device using the DBREQ, BAVL, TR, TDACK, ID [1:0],

and D [63:0] = DTR signals (handshake protocol using the data bus). A transfer request can also

be issued simply by asserting TR, without using the external bus (handshake protocol without use

of the data bus). For channel 2, after making the DMA transfer settings in the normal way, a

transfer request can be issued directly from an external device (with DBREQ, BAVL, TR,

TDACK, ID [1:0], and D [63:0] = DTR pins) by asserting DBREQ and TR simultaneously.

Note: DTR format = Data transfer request format

In DDT mode, there is a choice of five modes for performing DMA transfer.

device (with

and ID [1:0])

Rev. 6.0, 07/02, page 545 of 986

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