Table 8-14 Address Ranges Specifiable in MAR and IOAR
1-Mbyte Mode
16-Mbyte Mode
MAR
H'00000 to H'FFFFF
H'000000 to H'FFFFFF
(0 to 1048575)
(0 to 16777215)
IOAR
H'FFF00 to H'FFFFF
H'FFFF00 to H'FFFFFF
(1048320 to 1048575)
(16776960 to 16777215)
MAR bits 23 to 20 are ignored in 1-Mbyte mode.
8.6.8 Bus Cycle when Transfer is Aborted
When a transfer is aborted by clearing the DTE bit or suspended by an NMI that clears the DTME
bit, if this halts a channel for which the DMAC has a transfer request pending internally, a dead
cycle may occur. This dead cycle does not update the halted channel’s address register or counter
value. Figure 8-27 shows an example in which an auto-requested transfer in cycle-steal mode on
channel 0 is aborted by clearing the DTE bit in channel 0.
Figure 8-27 Bus Timing at Abort of DMA Transfer in Cycle-Steal Mode
ø
Address bus
RD
HWR
,
LWR
CPU cycle
DMAC cycle
CPU cycle
DMAC
cycle
CPU cycle
DTE bit is
cleared
T
1
T
2
T
d
T
1
T
2
T
1
T
2
T
1
T
2
T
3
T
d
T
d
T
1
T
2
241
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