================================================================
INITIALIZATION CONTROL WORDS (ICWs)
================================================================
Byte with b4=1 directed at I/O ports 20h or A0h is interpreted
as Initialization Control Word #1 (ICW1). ICW2 and ICW3 must be
sent immediately after sending ICW1. ICW4 is optional.

	  b7   b6   b5   b4   b3   b2   b1   b0		normal
	 ---------------------------------------	value:
ICW1	| A7 | A6 | A5 | 1  |LTIM|ADI |SNGL|IC4 |	11h
	 ---------------------------------------
A7:A5   (used for 8-bit 8080/8085 CPU only)
LTIM	1=level-triggered interrupt, 0=edge
ADI     (used for 8-bit 8080/8085 CPU only)
SNGL	1=single mode, 0=cascade (master or slave)
IC4	1=ICW4 needed, 0=ICW4 not needed

	  b7   b6   b5   b4   b3   b2   b1   b0		normal
	 ---------------------------------------	value:
ICW2	| T7 | T6 | T5 | T4 | T3 |A10 | A9 | A8 |	08h (BIOS; master)
	 ---------------------------------------	70h (BIOS; slave)
T7:T3	INT corresponding to lowest IRQ
A10:A8  (used for 8-bit 8080/8085 CPU only)

	  b7   b6   b5   b4   b3   b2   b1   b0		normal
ICW3	 ---------------------------------------	value:
master	| S7 | S6 | S5 | S4 | S3 | S2 | S1 | S0 |	04h
	 ---------------------------------------
S7:S0	1=slave on this IRQ input pin

	  b7   b6   b5   b4   b3   b2   b1   b0		normal
ICW3	 ---------------------------------------	value:
slave	| 0  | 0  | 0  | 0  | 0  | ID2| ID1| ID0|	02h
	 ---------------------------------------
ID2:ID0	slave ID (0-7)

	  b7   b6   b5   b4   b3   b2   b1   b0		normal
	 ---------------------------------------	value:
ICW4	| 0  | 0  | 0  |SFNM|BUF |M/S |AEOI|CPU |	01h
	 ---------------------------------------
SFNM	Special Fully Nested Mode (?)
BUF:M/S
	0x=non-buffered mode
	10=buffered mode slave
	11=buffered mode master
AEOI	1=automatic EOI, 0=normal EOI
CPU     1=x86, 0=8085

================================================================
OPERATION CONTROL WORDS (OCWs)
================================================================

I/O ports 21h, A1h:
	  b7   b6   b5   b4   b3   b2   b1   b0
	 ---------------------------------------
OCW1	| M7 | M6 | M5 | M4 | M3 | M2 | M1 | M0 |
	 ---------------------------------------
M7:M0	active low bit to enable corresponding IRQ

I/O ports 20h, A0h:
	  b7   b6   b5   b4   b3   b2   b1   b0		normal
	 ---------------------------------------	value:
OCW2	| H  | SL |EOI | 0  | 0  | L2 | L1 | L0 |	20h
	 ---------------------------------------
H:SL:EOI
	000=rotate in automatic EOI mode (clear)
	001=non-specific EOI			(<-- normal value)
	010=no operation
	011=specific EOI
	100=rotate in automatic EOI mode (set)
	101=rotate on non-specific EOI
	110=set priority [*]
	111=rotate on specific EOI [*]

L2-L0	IRQ level to be acted upon. Used only by [*]
	commands listed above.

I/O ports 20h, A0h:
	  b7   b6   b5   b4   b3   b2   b1   b0
	 ---------------------------------------
OCW3	| 0  |ESMM|SMM | 0  | 1  | P  | RR |RIS |
	 ---------------------------------------
	xxx
