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Single Address Mode
In single address mode, either the transfer source or transfer destination peripheral device is
accessed (selected) by means of the DACK signal, and the other device is accessed by address.
In this mode, the DMAC performs one DMA transfer in one bus cycle, accessing one of the
external devices by outputting the DACK transfer request acknowledge signal to it, and at the
same time outputting an address to the other device involved in the transfer. For example, in
the case of transfer between external memory and an external device with DACK shown in
figure 11.9, when the external device outputs data to the data bus, that data is written to the
external memory in the same bus cycle.
DMAC
SH7709S
DACK
DREQ
External address bus
External data bus
External
memory
External device
with DACK
Data flow
Figure 11.9 Data Flow in Single Address Mode
Two kinds of transfer are possible in single address mode: (1) transfer between an external device
with DACK and a memory-mapped external device, and (2) transfer between an external device
with DACK and external memory. In both cases, only the external request signal (
DREQ
) is used
for transfer requests.
Figures 11.10 and 11.11 show examples of DMA transfer timing in single address mode.
Содержание SH7709S
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Страница 292: ...273 T1 CKIO A25 to A0 CSn RD WR RD D31 to D0 WEn D31 to D0 BS T2 Read Write Figure 10 6 Basic Timing of Basic Interface ...
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