Datasheet

Section 7 DMA Controller (DMAC)
R01UH0309EJ0500 Rev. 5.00 Page 383 of 1408
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
DREQ pin sampling is performed every cycle, with the rising edge of the next φ cycle after the
end of the DMABCR write cycle for setting the transfer enabled state as the starting point.
When the DREQ pin low level is sampled while acceptance by means of the DREQ pin is
possible, the request is held in the DMAC. Then, when activation is initiated in the DMAC, the
request is cleared, and DREQ pin high level sampling for edge detection is started. If DREQ pin
high level sampling has been completed by the time the DMA write cycle ends, acceptance
resumes after the end of the write cycle, DREQ pin low level sampling is performed again, and
this operation is repeated until the transfer ends.