Register During Dma Transfer - Renesas H8SX/1500 Series Hardware Manual

Section 7 DMA Controller (DMAC)
7.4.7

Register during DMA Transfer

The DMAC registers are updated by a DMA transfer. The value to be updated differs according to
the other settings and transfer state. The registers to be updated are DSAR, DDAR, DTCR, bits
BKSZH and BKSZ in DBSR, and the DTE, ACT, ERRF, ESIF, and DTIF bits in DMDR.
(1)
DMA Source Address Register
When the transfer source address set in DSAR is accessed, the contents of DSAR are output and
then are updated to the next address.
The increment or decrement can be specified by bits SAT1 and SAT0 in DACR. When SAT1 and
SAT0 = B'00, the address is fixed. When SAT1 and SAT0 = B'01, the address is added with the
offset. When SAT1 and SAT0 = B'10, the address is incremented. When SAT1 and SAT0 = B'11,
the address is decremented. The size of increment or decrement depends on the data access size.
The data access size is specified by bits DTSZ1 and DTSZ0 in DMDR. When DTSZ1 and DTSZ0
= B'00, the data access size is byte and the address is incremented or decremented by 1. When
DTSZ1 and DTSZ0 = B'01, the data access size is word and the address is incremented or
decremented by 2. When DTSZ1 and DTSZ0 = B'10, the data access size is longword and the
address is incremented or decremented by 4. Even if the access data size of the source address is
word or longword, when the source address is not aligned with the word or longword boundary,
the read bus cycle is divided into byte or word cycles. While data of one word or one longword is
being read, the size of increment or decrement is changing according to the actual data access size,
for example, +1 or +2 for byte or word data. After one word or one longword of data is read, the
address when the read cycle is started is incremented or decremented by the value according to
bits SAT1 and SAT0.
In block or repeat transfer mode, when the block or repeat size of data transfers is completed while
the block or repeat area is specified to the source address side, the source address returns to the
transfer start address and is not affected by the address update.
When the extended repeat area is specified to the source address side, operation follows the
setting. The upper address bits are fixed and is not affected by the address update.
While data is being transferred, DSAR must be accessed in longwords. If the upper word and
lower word are read separately, incorrect data may be read from since the contents of DSAR
during the transfer may be updated regardless of the access by the CPU. Moreover, DSAR for the
channel being transferred must not be written to.
Rev. 3.00 Mar. 14, 2006 Page 176 of 804
REJ09B0104-0300