Tandy 1000 SL Technical Reference Manual page 42

Address Description
0020 8259A Interrupt Controller
Note: Initialization words are set up by the operating system and
are generally not to be changed. Writing an initialization
word might cancel pending interrupts.
Bit 4 =
1
Initialization Command Word
1
Bit
0
0
ICW4 Needed
1
ICW4 Not Needed
Bit
1
0
Cascade Mode
1 Single Mode
Bit 2 Not Used
Bit
3
0
Edge Triggered Mode
1 Level Triggered Mode
Bits
5-7
Not Used
Bit
4
= 0
Operation Control Word 2
Bit
3 = 0
BitO-2: Determine The Interrupt Level
Acted On When the SL Bit Is Active
Interrupt Level =
0
1 2
3 4 5 6 7
Bit
0
(LO):
0
1 0
1 0
1 0
1
Bit
1
(Ll):
0 0
1
1 0 0
1 1
Bit 2 (~2):
0 0 0 0 1 1
1 1
Bits
5-7:
Control Rotate and End of Interrupt Modes
B7 B6 B5
0 0 1
0 1 1
1 0 1
1 0 0
0 0 0
1 1 1
1 1 0
0 1 0
Non-Specific EO1 Command End Of Interrupt
Specific EO1 Command ? & d Of Interrupt
Rotate On Non-Specific EO1 Auto Rotation
Rotate In Automatic EO1 Mode (Set) Auto Rotation
Rotate In Automatic EO1 Mode (Clear) Auto Rotation
*Rotate On Specific EO1 Command Specific Rotation
*
Set Pr
i
or i t
y
Command Specific Rotation
No Operation
(*LO
-
L2 Are Used)
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