-- Lark8255.txt
-- L. Stewart  December 16, 1981  10:40 PM

8255 Programming:

Port	Write		Read
-------------------------------
D0	Port A		Port A
D1	Port B		Port B
D2	Port C		Port C
D3	Control		unused

Control word  88   (to port D3) sets up Ports A, B, and C0-3
as outputs and port C4-7 as input.

Port A  output, unused

Port B  output
--------------------
0	KickWDT
1	StopAudClk'
2	PTimerStart
3
4
5
6
7

Port C 0-3
--------------------
0	Key/Dat'
1	Encrypt/Decrypt'
2	StartEncrypt
3	ResetEncInt'

Port C 4-7
--------------------
4
5	EncPar
6	EncBusy'
7	EncCP'

Port B control words of immediate interest:

Port D1

00	Turn off timer clock
02	Turn on timer clock
	Lower PTimerStart
06	Raise PTimerStart

-- Standard setup, leaving timer clock off
OD3,88
OD1,00

-- Turn on timer clock or Lower PTimerStart
OD1,02

-- Raise PTimerStart
OD1,06