Rev. 1.0, 09/01, page 333 of 904
Address bus
ø
EXDMA
read cycle
EXDMA
write cycle
EDSAR
EDDAR
Figure 8.2 Example of Timing in Dual Address Mode
Single Address Mode: In single address mode, the
('$&.
signal is used instead of the source or
destination address register to transfer data directly between an external device and external
memory. In this mode, the EXDMAC accesses the transfer source or transfer destination external
device by outputting the external I/O strobe signal (
('$&.
), and at the same time accesses the
other external device in the transfer by outputting an address. In this way, DMA transfer can be
executed in one bus cycle. In the example of transfer between external memory and an external
device with DACK shown in figure 8.3, data is output to the data bus by the external device and
written to external memory in the same bus cycle.
The transfer direction, that is whether the external device with DACK is the transfer source or
transfer destination, can be specified with the SDIR bit in EDMDR. Transfer is performed from
the external memory (EDSAR) to the external device with DACK when SDIR = 0, and from the
external device with DACK to the external memory (EDDAR) when SDIR = 1.
The setting in the source or destination address register not used in the transfer is ignored.
The
('$&.
pin becomes valid automatically when single address mode is selected. The
('$&.
pin is active-low.
(7(1'
pin output can be enabled or disabled by means of the ETENDE bit in
EDMDR.
(7(1'
is output for one bus cycle.
Figure 8.3 shows the data flow in single address mode, and figure 8.4 shows an example of the
timing.
Summary of Contents for H8S/2376 F-ZTAT
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