Archive of the former Yahoo!Groups mailing list: Homebrew PCBs
Subject: CNC controller - port pin pullups/downs?
From: "ghidera2000" <ghidera2000@...>
Date: 2003-10-12
I'm just finishing up the design for an A3977SED based controller
board but I'm a bit confused about the parallel port connections.
Can the parallel port drive logic high and low or does it just go
active low (sinking) and high-Z? i.e. Do I need pullups to generate
logic high, or can the parallel port handle this just fine?
I plan on pulling Enable high on the board and setting it to active
low in the software. That way if the cable pops out I know the
drives will stop.