4014 emulator drops out of plot mode sometimes

[laser-lovers@uw-beaver]

From: l5!g...@lll-crg.arpa (John Gilmore)

Early versions of the Sun ROM Monitor had an incomplete 4014 emulation
mode with a similar problem. The 4014 manual does not say what happens
if you feed it an undefined control character (eg ^V). The emulator
was dropping out of plot mode when it saw these. The real 4014
does not. Various graphics programs have gotten used to the idea that
they can send random control characters to a "4014" and they will get
ignored. This has to be noticed by emulator writers, many of whom
just start with the manual and few or no test cases.