Hidden Device?

[droopy 0]

Hi, I am working with GX Works2, GT Designer 3 and an FX3U plc. I've been trying to modify a program in order to add extra logins so we can have a unique username and password for each user of a machine (it only came with slots for 10 users). In the GOT program there is a login screen with two ASCII input fields: Username (D1) and Password (D2). I can find the username device on a rung in the ladder program but not the password device. They both appear in the device list but D2 is shown as having no contact. Does anyone have any advice on how to locate this device in the ladder? Could this be some sort of obfuscation from the manufacturer? A possible clue: a cross-reference search for D2 returns D1. Thanks Edited 20 Nov 2013 by droopy

[bakkerfrits 0]

Hello Droopy, I have send you a PM.

[JRoss 84]

32-bit (double) instructions require two adjacent data registers. Probably the code is looking at username and password as a single double word. What are the instructions referencing D1? @ bakkerfrits - the point of a forum is so that everybody can be part of and learn from the conversation.

[droopy 0]

I had simplified the register names--it's actually D121 for username and D125 for password. Each one can be up to 8 characters so each requires 4 registers. The instruction referencing D121 (it's executed when the login button is pressed) is a character string search which looks for a match between the username entered by the user and the usernames stored in memory. Am I allowed to post snippets of the actual program if I didn't write it? RE: the cross reference match, it appears to be due to a FMOV instruction which applies to D121 through D125, filling them all with H2020.

[JRoss 84]

Sounds very like some code I wrote for one of my customers. H2020 is the hex code for two space characters. Look for an INSTR instruction that searches for the username/password registers in an array of username/passwords combinations. Edit: I forgot to answer your question about posting code. If the code is proprietary in any way, protected by licensing or a non-disclosure agreement, then you should not post the program. Screen shots of small pieces of a program don't really pose a problem, however. Edited 21 Nov 2013 by JRoss