•
TANDY COMPUTER PRODUCTS •
48
OOOA
Bit
0-1
2
3-7
OOOB
Bit
0-1
2-3
4
5
6-7
oooc
DMA Controller
IOW*
=
0
f
Write Single Mask Register
Description
Bitl BitO
0
0
Select channel 0 mask bit
0
1
Select channel 1 mask bit
1
0
Select channel 2 mask bit
1
1
Select channel 3 mask bit
0 Clear mask bit (Disable Channel)
1 Set mask bit (Disable Channel)
Don't care
IOR*
=
0, Illegal
DMA Controller
IOW*
=
0
f
Write Mode Register
Description
Bitl BitO
0
0
Channel
0
select
0
1
Channel
1
select
1
0
Channel
2
select
1
1
Channel
3
select
Bit3 Bit2
0
0
Verify transfer
0
1
Write transfer to memory
1
0
Read transfer to memory
1
1
Illegal
X If bits
6
and 7
=
11
0 Autoinitialization disable
1 Autoinitialization enable
0 Address increment select
1 Address decrement select
Bit7 Bit6
0
0
Demand mode select
0
1
Single mode select
1
0
Block mode select
1
1
Cascade mode select
IOR*
=
0, Illegal
DMA Controller
IOW*
=
0, Clear Byte Pointer Flip/Flop
IOR*
=
0, Illegal
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