SH7014 datasheet(181/754 Pages) RENESAS

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9. Direct Memory Access Controller (DMAC)

Rev.5.00 Sep. 27, 2007 Page 147 of 716

REJ09B0398-0500

Section 9 Direct Memory Access Controller (DMAC)

9.1

Overview

The SH7014 includes an on-chip two-channel direct memory access controller (DMAC). The

DMAC can be used in place of the CPU to perform high-speed data transfers among external

devices equipped with DACK (transfer request acknowledge signal), external memories, memory-

mapped external devices, and on-chip peripheral modules (except for the DMAC and BSC). Using

the DMAC reduces the burden on the CPU and increases operating efficiency of the LSI as a

whole.

9.1.1

Features

The DMAC has the following features:

• Two channels

• Four Gbytes of address space in the architecture

• Byte, word, or longword selectable data transfer unit

• 64 k (65,536) transfers

• Single or dual address mode.

⎯ Single address mode: Either the transfer source or transfer destination (peripheral device) is

accessed by a DACK signal while the other is accessed by address. One transfer unit of

data is transferred in each bus cycle.

⎯ Dual address mode: Both the transfer source and transfer destination are accessed by

address. Values set in a DMAC internal register indicate the accessed address for both the

transfer source and transfer destination. Two bus cycles are required for one data transfer.

• Channel function: Dual address mode and single address mode external requests can be

accepted.

• Transfer requests: There are three DMAC transfer activation requests, as indicated below.

⎯ External request: From two DREQ pins. DREQ can be detected either by falling edge or by

low level. These can be received by all channels.

⎯ Requests from on-chip peripheral modules: Transfer requests from on-chip modules such

as SCI or A/D. These can be received by all channels.

⎯ Auto-request: The transfer request is generated automatically within the DMAC.

• Selectable bus modes: Cycle-steal mode or burst mode

• The DMAC priority order is fixed at 0 > 1.

SH7014 Datasheet(PDF) 181 Page - Renesas Technology Corp