r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 344

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 7 DMA Controller (DMAC)
IOAR can be used in short address mode but not in full address mode.
7.3.3
ETCR is a 16-bit readable/writable register that specifies the number of transfers.
The DMA has four ETCR registers: ETCR_0A in channel 0 (channel 0A), ETCR_0B in channel 0
(channel 0B), ETCR_1A in channel 1 (channel 1A), and ETCR_1B in channel 1 (channel 1B).
ETCR is not initialized by a reset or in standby mode.
(1)
The function of ETCR in sequential mode and idle mode differs from that in repeat mode.
In sequential mode and idle mode, ETCR functions as a 16-bit transfer counter. ETCR is
decremented by 1 each time a transfer is performed, and when the count reaches H'00, the DTE bit
in DMABCRL is cleared, and transfer ends.
In repeat mode, ETCRL functions as an 8-bit transfer counter and ETCRH functions as a transfer
count holding register. ETCRL is decremented by 1 each time a transfer is performed, and when
the count reaches H'00, ETCRL is loaded with the value in ETCRH. At this point, MAR is
automatically restored to the value it had when the count was started. The DTE bit in DMABCRL
is not cleared, and so transfers can be performed repeatedly until the DTE bit is cleared by the
user.
(2)
The function of ETCR in normal mode differs from that in block transfer mode.
In normal mode, ETCRA functions as a 16-bit transfer counter. ETCRA is decremented by 1 each
time a data transfer is performed, and transfer ends when the count reaches H'0000. ETCRB is not
used in normal mode.
In block transfer mode, ETCRA functions as an 8-bit block size counter (ETCRAL) and ETCRAH
functions as a block size holding register. ETCRAL is decremented by 1 each time a 1-byte or 1-
word transfer is performed, and when the count reaches H'00, ETCRAL is loaded with the value in
ETCRAH. So by setting the block size in ETCRAH and ETCRAL, it is possible to repeatedly
transfer blocks consisting of any desired number of bytes or words.
Rev. 1.00 Sep. 19, 2008 Page 314 of 1342
REJ09B0467-0100
Short Address Mode
Full Address Mode
Execute Transfer Count Registers (ETCRA and ETCRB)