H8SXSLASH1663R datasheet(531/1504 Pages) RENESAS

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Section 11 EXDMA Controller (EXDMAC)

Rev. 2.00 Sep. 24, 2008 Page 499 of 1468

REJ09B0412-0200

(3)

Offset subtraction specification

To set a negative value in EDOFR, specify a twos complement as an offset value. A twos

complement is derived by the following expression:

[Twos complement expression for negative offset value] =

−[offset value] + 1 (−: bit reverse)

Example: Twos complement expression of H'0001FFFF

= H'FFFE0000 + H'00000001

= H'FFFE0001

A twos complement can be derived by the NEG.L instruction of the CPU.

11.5.7

Registers during EXDMA Transfer Operation

EXDMAC register values are updated as EXDMA transfer processing is performed. The updated

values depend on various settings and the transfer status. The following registers and bits are

updated: EDSAR, EDDAR, EDTCR, bits BKSZH and BKSZ in EDBSR, and bits DTE, ACT,

ERRF, ESIF and DTIF in EDMDR.

(1)

EXDMA Source Address Register (EDSAR)

When the EDSAR address is accessed as the transfer source, the EDSAR value is output, and then

EDSAR is updated with the address to be accessed next.

Bits SAT1 and SAT0 in EDACR specify incrementing or decrementing. The address is fixed

when SAT1 and SAT0 = B

′00, incremented by offset register value when SAT1 and SAT0 =

′01, incremented when SAT1 and SAT0 = B′10, and decremented when SAT1 and SAT0 =

′11. (The increment or decrement value is determined by the data access size.)

The DTSZ1 and DTSZ0 bits in EDMDR set the data access size. When DTSZ1 and DTSZ0 =

′00, the data is byte-size and the address is incremented or decremented by 1. When DTSZ1 and

DTSZ0 = B

′01, the data is word-size and the address is incremented or decremented by 2. When

DTSZ1and DTSZ0 = B

′10, the data is longword-size and the address is incremented or

decremented by 4. When a word-size or longword-size is specified but the source address is not at

the word or longword boundary, the data is divided into bytes or words for reading. When a word

or longword is divided for reading, the address is incremented or decremented by 1 or 2 according

to an actual byte-or word-size read. After a word-size or longword-size read, the address is

incremented or decremented to or from the read start address according to the setting of SAT1 and

SAT0.

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