208
DMAC (R): DMAC read cycle
DMAC (W): DMAC write cycle
CK
DREQ
DACK
Bus cycle
T2
Tw
T1
CPU
CPU
DMAC (R)
CPU
CPU
T2
Tw
T1
CPU
DMAC (W)
Figure 9.18
DREQ
Sampling Timing in Cycle-Steal Mode (Output with
DREQ
Level
Detection and DACK Active-Low) (Dual Address Mode, Bus Cycle = 2 1 Wait State)
CK
DREQ
DACK
Bus cycle
Tc
Tr
Tp
Tc
CPU
CPU
CPU
DMAC
CPU
CPU
Tc
Tr
Tp
Tc
DMAC
Note:
When
DREQ
is negated at the fourth state of the DMAC cycle, the next DMA transfer will
be executed because the sampling is performed at the second state of the DMAC cycle.
Figure 9.19
DREQ
Sampling Timing in Cycle-Steal Mode (Output with
DREQ
Level
Detection and DACK Active-Low) (Single Address Mode, Bus Cycle = DRAM Bus Cycle
(Long Pitch Normal Mode))
Содержание HD6417032
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