r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 437

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 8 EXDMA Controller (EXDMAC)
In block transfer mode, a transfer of the specified block size is executed in response to one transfer
request. The block size can be from 1 to 256 bytes or words. Within a block, transfer can be
performed at the same high speed as in block transfer mode.
When the “no specification” setting (EDTCR = H'000000) is made for the number of transfers, the
transfer counter is halted and there is no limit on the number of transfers, allowing transfer to be
performed endlessly.
Incrementing or decrementing the memory address by 1 or 2, or leaving the address unchanged,
can be specified independently for each address register.
In all transfer modes, it is possible to set a repeat area comprising a power-of-two number of
bytes.
8.4.2
Address Modes
(1)
Dual Address Mode
In dual address mode, both the transfer source and transfer destination are specified by registers in
the EXDMAC, and one transfer is executed in two bus cycles.
The transfer source address is set in the source address register (EDSAR), and the transfer
destination address is set in the transfer destination address register (EDDAR).
In a transfer operation, the value in external memory specified by the transfer source address is
read in the first bus cycle, and is written to the external memory specified by the transfer
destination address in the next bus cycle.
These consecutive read and write cycles are indivisible: another bus cycle (external access by an
internal bus master, refresh cycle, or external bus release cycle) does not occur between these two
cycles.
ETEND pin output can be enabled or disabled by means of the ETENDE bit in EDMDR. ETEND
is output for two consecutive bus cycles. The EDACK signal is not output.
Figure 8.2 shows an example of the timing in dual address mode.
Rev. 1.00 Sep. 19, 2008 Page 409 of 1270
REJ09B0466-0100