SH7205 Datasheet, PDF (432/1904 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 11 Direct Memory Access Controller (DMAC)
Initial
Bit
Bit Name Value R/W Description
16
DREQ 0
R/W DMA Request
This bit enables you to check whether a DMA request is
currently present. If the software trigger (DCTG = 000000) is
selected by the DMA request source select bits (DCTG), use
this bit to operate DMA requests.
0: DMA request not currently present
1: DMA request currently present
The value of this bit varies with the status of the DMA request
signal input to the DMAC regardless of the settings of the
DMAC module activate bit (DMST) and DMA transfer enable bit
(DEN). The setting and clearing conditions of this bit vary with
the settings of the DMA request source select bits (DCTG) and
input sense mode select bits (STRG) as described below.
(a) When the software trigger is selected by the DMA request
source select bits (DCTG)
• Setting condition
This bit is set to 1 when software writes 1 to the bit. This
generates a DMA request.
• Clearing condition
This bit is cleared to 0 when any of the following conditions
is met:
 Software writes 0 to this bit.
 Operand transfer is started that corresponds to this bit.
(b) When a request source other than the software trigger is
selected by the DMA request source select bits (DCTG)
and a level sense is selected
• Setting condition
This bit is set to 1 when the DMA request signal input level
matches that specified in the input sense mode select bits
(STRG), i.e. when a DMA request exists.
• Clearing condition
This bit is cleared to 0 when the level set in the input sense
mode select bits (STRG) does not match the DMA request
signal input level, i.e. when no DMA request exists.
If a DMA request disappears before being accepted, it is not
retained and the DMA request bit (DREQ) is cleared to 0. For
this reason, to use the DMA request with a level sense, retain
the request till it is accepted.
Rev. 1.00 Mar. 25, 2008 Page 400 of 1868
REJ09B0372-0100