
DMASH20A_010020020700
Rev. 2.0, 09/02, page 149 of 732
Section 10 Direct Memory Access Controller (DMAC)
This LSI includes an on-chip four-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, DTC, BSC, and UBC).
Using the DMAC reduces the burden on the CPU and increases operating efficiency of the LSI as
a whole.
10.1
Features
Four channels
Four Gbytes of address space in the architecture
Byte, word, or longword selectable data transfer unit
16,777,216 transfers, maximum
Address mode
Dual address mode or single address mode can be selected.
Direct access or indirect access can be selected in dual address mode.
Channel function: Transfer modes that can be set are different for each channel.
Channel 0: Single or dual address mode. External requests are accepted.
Channel 1: Single or dual address mode. External requests are accepted.
Channel 2: Dual address mode only. Source address reload function is available.
Channel 3: Dual address mode only. Direct address transfer mode and indirect address
transfer mode selectable.
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.
Requests from on-chip peripheral modules: Transfer requests from on-chip modules such
as SCI (request made to SCI_0 and SCI_1) or A/D (request made to A/D 1).
Auto-request: The transfer request is generated automatically within the DMAC.
Selectable bus modes: Cycle-steal mode or burst mode
Two types of DMAC channel priority ranking: Fixed priority mode or round robin mode
CPU can be interrupted when the specified number of data transfers are complete.
Module standby mode can be set.