Dma Transfer Types - Hitachi SH7032 Hardware Manual

9.3.4

DMA Transfer Types

The DMAC supports the transfers shown in table 9.5. It can operate in single address mode or dual
address mode, which are defined by how many bus cycles the DMAC takes to access the transfer
source and transfer destination. The actual transfer operation timing varies with the bus mode. The
DMAC has two bus modes: cycle-steal mode and burst mode.
Table 9.5 Supported DMA Transfers
Source
External device with
DACK
External memory
Memory-mapped external
device
On-chip memory
On-chip supporting
module
Single: Single address mode
Dual: Dual address mode
Address Modes:
• Single Address Mode
In single address mode, both the transfer source and destination are external; one (selectable) is
accessed by a DACK signal while the other is accessed by an address. In this mode, the
DMAC performs the DMA transfer in 1 bus cycle by simultaneously outputting a transfer
request acknowledge DACK signal to one external device to access it while outputting an
address to the other end of the transfer. Figure 9.6 shows an example of a transfer between an
external memory and an external device with DACK in which the external device outputs data
to the data bus while that data is written in external memory in the same bus cycle.
External
Device with External
DACK Memory
Not available Single
Single Dual
Single Dual
Not available Dual
Not available Dual
Destination
Memory-
Mapped
External On-Chip
Device Memory
Single Not available
Dual Dual
Dual Dual
Dual Dual
Dual Dual
On-Chip
Supporting
Module
Not available
Dual
Dual
Dual
Dual
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