SH7080 Datasheet, PDF (236/1644 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 8 Data Transfer Controller (DTC)
8.2.5 DTC Transfer Count Register A (CRA)
CRA is a 16-bit register that designates the number of times data is to be transferred by the DTC.
In normal transfer mode, CRA functions as a 16-bit transfer counter (1 to 65,536). It is
decremented by 1 every time data is transferred, and bit DTCEn (n = 15 to 0) corresponding to the
activation source is cleared and then an interrupt is requested to the CPU when the count reaches
H'0000. The transfer count is 1 when CRA = H'0001, 65,535 when CRA = H'FFFF, and 65,536
when CRA = H'0000.
In repeat transfer mode, CRA is divided into two parts: the upper eight bits (CRAH) and the lower
eight bits (CRAL). CRAH holds the number of transfers while CRAL functions as an 8-bit
transfer counter (1 to 256). CRAL is decremented by 1 every time data is transferred, and the
contents of CRAH are sent to CRAL when the count reaches H'00. The transfer count is 1 when
CRAH = CRAL = H'01, 255 when CRAH = CRAL = H'FF, and 256 when CRAH = CRAL =
H'00.
In block transfer mode, CRA is divided into two parts: the upper eight bits (CRAH) and the lower
eight bits (CRAL). CRAH holds the block size while CRAL functions as an 8-bit block-size
counter (1 to 256 for byte, word, or longword). CRAL is decremented by 1 every time a byte
(word or longword) data is transferred, and the contents of CRAH are sent to CRAL when the
count reaches H'00. The block size is 1 byte (word or longword) when CRAH = CRAL =H'01,
255 bytes (words or longwords) when CRAH = CRAL = H'FF, and 256 bytes (words or
longwords) when CRAH = CRAL =H'00.
CRA cannot be accessed directly from the CPU.
Bit: 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
Initial value: *
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
R/W: -
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
* : Undefined
Rev. 3.00 May 17, 2007 Page 178 of 1582
REJ09B0181-0300