
UM008101-0601 Direct Memory Access
REGISTER BIT FUNCTIONS
Write Register Bit Functions
Figure 76. Write Register 0 Group
Figure 77. Write Register 1 Group
D7 D6 D5 D4 D3 D2 D1 D0
Base Register Byte
Port A Starting Address
00
0
1
1
1
0
1
Do not use
=Transfer
=Search
= Search/Transfer
0
=PortB
→ Port A
0
=PortA
→ Port B
(Low Byte)
Port A Starting Address
(High Byte)
Block Length
(Low Byte)
Block Length
(High Byte)
D7
D6 D5 D4 D3 D2 D1 D0
Base Register Byte
00
0
1
1
1
0
1
= Port A Address Decrements
0
= Port A is Memory
0
= Port A is I/O
Port A Variable
00
0
1
1
1
0
1
= Cycle Length = 3
= Cycle Length = 2
=DoNotUse
= Port A Address Increments
= Port A Address Fixed
Timing Byte
= Cycle Length = 4
WR
Ends 1/2 Cycle Early = 0
RD
Ends 1/2 Cycle Early = 0
MREQ
Ends 1/2 Cycle Early = 0 0 = IORQ Ends 1/2 Cycle Early
00
0010
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