Dma Control Registers (Dmacra And Dmacrb) - Renesas H8S/2368 Series Hardware Manual

Short Address Mode: 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.
Full Address Mode: 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, ETCRAL functions as an 8-bit block size counter 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.
In block transfer mode, ETCRB functions as a 16-bit block transfer counter. ETCRB is
decremented by 1 each time a block is transferred, and transfer ends when the count reaches
H'0000.
7.3.4

DMA Control Registers (DMACRA and DMACRB)

DMACR controls the operation of each DMAC channel.
The DMA has four DMACR registers: DMACR_0A in channel 0 (channel 0A), DMACR_0B in
channel 0 (channel 0B), DMACR_1A in channel 1 (channel 1A), and DMACR_1B in channel 1
(channel 1B).
In short address mode, channels A and B operate independently, and in full address mode,
channels A and B operate together. The bit functions in the DMACR registers differ according to
the transfer mode.
Rev. 2.00, 05/03, page 204 of 820