Datasheet

Section 8 EXDMA Controller
Rev. 3.00 Mar 17, 2006 page 352 of 926
REJ09B0283-0300
Address bus
φ
RD
WR
ETEND
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 EDACK 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 (EDACK), 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 EDACK pin becomes valid automatically when single address mode is selected. The EDACK
pin is active-low. ETEND pin output can be enabled or disabled by means of the ETENDE bit in
EDMDR. ETEND 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.