Tandy 1000 HX Technical Reference Manual page 53

• 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