-- Lark8259.txt
-- L. Stewart  8-Dec-81 11:20:51

Interrupt controller ports

50 and 51

Interrupts:
-------------------
0	Audio Input
1	SLC Receive
2	SLC Transmit
3	Encryption
4	8274
5	Timer
6	---
7	---

Initialization of 8259A

-- ICW1, level triggered, single 8259, ICW4 needed
O50,1B

-- ICW2, vector = 20-27  (interrupts at 80-9C )
O51,20

-- ICW4, not special nested, not buffered, auto EOI, 8088 mode
O51,03

-- OCW1,  all masked but timer
O51,DF

-- OCW2, (not needed for anything)
O50,40	NOP
O50,20	Non-specific EOI

-- OCW3, no special mask mode, alternatives:
O50,0C	Poll (next read will be 80+interrupt level)
O50,0A	next read will be IR register
O50,0B	next read will be IS register

--  Initialization sequence
O50,1B
O51,20,03,DF

--  Allow Aud int OR TimerInt
O50,1B
O51,20,03,DE