SH7261 Datasheet, PDF (346/1348 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7260 Series

Section 11 Direct Memory Access Controller (DMAC)
11.3.3 DMA Current Byte Count Register (DMCBCT)
DMCBCT is a register used to specify the number of bytes to be transferred by DMA.
The value in this register is transferred to the working byte-count register at the start of DMA
transfer, and is then decremented by the number of bytes transferred on each unit data transfer.
Decrementation is thus by the following values.
• When the transfer size is set to 8 bits (SZSEL = "000"): −1
• When the transfer size is set to 16 bits (SZSEL = "001"): −2
• When the transfer size is set to 32 bits (SZSEL = "010"): −4
When the value in the working byte count register reaches H'000 0000, DMA transfer ends (an
end due to byte count "0"). The corresponding bit of the DMA transfer end detection register
(DMEDET) is set to 1.
If the byte count reload function is disabled, the contents of the working byte count register are
returned to this register at the moment the channel for DMA transfer switches or DMA transfer
ends. If the byte count reload function is enabled, the contents of the DMA reload byte counter
register (DMRBCTn) are returned to this register.
This register must be set before transfer is initiated, regardless of whether the reload function is
enabled or disabled.
Bit: 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
——————
CBC
Initial value: 0
0
0
0
0
0 ——————————
R/W: R R R R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
Bit: 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
CBC
Initial value: — — — — — — — — — — — — — — — —
R/W: R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
Initial
Bit
Bit Name Value
R/W Description
31 to 26 
All 0
R
Reserved
These bits are always read as 0. The write value
should always be 0.
25 to 0 CBC
Undefined R/W Number of bytes to be DMA-transferred.
Notes: 1. Note that a setting of H'000 0000 leads to transfer of the maximum number of bytes, i.e.
64 Mbytes.
Rev. 2.00 Sep. 07, 2007 Page 314 of 1312
REJ09B0320-0200