Tandy 1400LT Service Manual page 270

F. DESCRIPTION OF I/O COMMANDS
B l t
Device Address Map
DMA CONTROLLER
0
o/
1 Clear/Set mask bit of channel 0
Address
Bit data
Description
O8H
(Command-Register)
0
o/
1
Memory to memory transfer disable/enable
1
o/
1
X
Channel 0 address hold disable/enable
[n case of bit O=O
2
o/
1 Controller enable/disable
3
o/
1
X
Normal/Compressed timing
In case of bit
O= 1
4
o/
1
Fixed/Rotating Priority
5
0
1
X
Normal write pulse
Extended write selection
In case of bit 3 = 1
DREQ sense active high/low
DACK sense active high/low
6
7
o/
1
0/1
09H
(Request-Register)
00
01
10
11
Selection of channel 0
Selection of channel 1
Selection of channel 2
Selection of channel 3
Preset/Set of request bit
2
o/
1
3 - 7
X X
Selection of mask bit of channel 0
Selection of mask bit of channel 1
Selection of mask bit of channel 2
Selection of mask bit of channel 3
OAH
(Mask-Register)
00
01
10
11
o/
1
Clear/Set of mask bit
2
X
3 - 7
I
x
Clear/Set mask bit of channel 1
1
I
0/1
2
I
o / l
Clear/Set mask bit of channel 2
3
I
0/1
I
Clear/Set mask bit of channel 3
F- 1