HD6412373R RENESAS [Renesas Technology Corp], HD6412373R Datasheet - Page 352

• Manufacturer Part Number: HD6412373R
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 7 DMA Controller (DMAC)
7.3.3
Execute Transfer Count Registers (ETCRA and ETCRB)
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.
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.
Rev.7.00 Mar. 18, 2009 page 284 of 1136
REJ09B0109-0700