Notes on the flexo interface
29 Oct 03

From the interface side, it appears to be a six-bit parallel
interface with busy/done handshake.

BUSY, asserted by the data presenter, starts the process.
The recipient asserts DONE which clears BUSY and readies for
the next transfer.

The machine blocks in phase1 until completion of the output cycle.
Hardware page 3-40 states CR, TAB, BS blocks until completion; 
this means either other characters complete in one machine cycle,
or ?


INPUT: When the input command I is given, a START READ signal is issued
and characters are inserted into shift-right A until a STOP READ command is 
received (see below). I take it this is to improve multi-character input
in an incredibly slow machine.

A STOP READ signal seems to be generated by a stunt-box-like function that
matches an apostrophe character, or the "START COMPUTE" or "STOP READ" switch
is pressed. (Maybe this works only with the keyboard? And ' characters
are required on tape?)

[Does this mean that typewriter input requires flipping the "START
COMPUTE" switch or typing ' after every input?!]