HP 7220C plotter port settings

Jules Richardson jules.richardson99 at gmail.com
Thu Dec 5 17:34:03 CST 2019

Hi all,

I picked up an HP 7220C flatbed plotter the other day which (after freeing 
the stuck carriage) is responding to panel commands in 'local' mode. For 
the terminal RS-232 interface, does anyone happen to know:

a) The character size (7 or 8 bits)?

b) If the connection between terminal and plotter is supposed to be 
straight through (i.e. 1:1 pin mapping), null modem, or something else 

I'm not sure if the plotter considers itself DTE or DCE, given that it has 
a modem output port (i.e. it sits partway along in the chain of things).

Oh, there's a "conf test" switch setting on the back - does anyone know the 
purpose of that? I'm wondering if it's supposed to echo back to the 
terminal any data that's sent to the plotter, but that's purely a guess. 
Sadly there don't seem to be any docs online (or much in the way of any 
info, to be honest).



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