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Chapter 15
DMA Functions (DMA Controller)
User’s Manual U16702EE3V2UD00
Figure 15-10:
DMA Channel Control Register (DMCHCn) Format (3/4)
(b) ACF bit status in channel-fixed single transfer mode
DMBC0 = 02H (3-times transfer)
DMBC3 = 03H (4-times transfer)
(c) ACF bit status in block transfer mode
DMBC0 = 02H (3-times transfer)
DMBC3 = 03H (4-times transfer)
DMARQ0
DMARQ3
DMA3
CPU
CPU
DMA3
CPU
DMA3
CPU
DMA3
CPU
DMA0
CPU
DMA0
CPU
DMA0
Bus status
CPU
TC
TC
CPU
CPU
Set to 1 by Software
Set to 1 by Software
ACF
(DMA channel 0)
EN
(DMA channel 0)
EN
(DMA channel 3)
ACF
(DMA channel 3)
DMARQ0
DMARQ3
DMA3
CPU
DMA3
DMA3
DMA3
CPU
CPU
DMA0
DMA0
DMA0
CPU
CPU
Bus status
TC
CPU
CPU
Set to 1 by Software
Set to 1 by Software
In this example, the internal bus is occupied by the DMA during these times.
Due to this behavior, the ACF bit during these times cannot be read by the CPU.
If a NMI interrupt occurs during a block transfer mode, then the ACF bit will be read by CPU as an “1”.
TC
ACF
(DMA channel 0)
EN
(DMA channel 0)
EN
(DMA channel 3)
ACF
(DMA channel 3)
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