Calling SY/MAX 400 users


Thread Starter

Ken Roach

Hello List,

I have a customer with a Sy/Max model 400 controller and a METRA 1010B
operator interface terminal.

The terminal is obsolete and they don't know much about the Sy/Max that has been running there for years either. Right now the priority is to
replace the operator interface terminal. Does anyone know what protocol the serial ports (there are two) on the Sy/Max 400 use? I'd love to use a PanelView to replace the Metra OIT but the closest thing A-B has is a Modbus driver.

Thanks in advance,

Ken Roach
Rockwell Automation / Seattle
[email protected]

George Graziano

The 2 com ports on the 400 are RS422 (just need a RS422 to RS232 converter if necessary). Not sure if your looking for Color, Monochrome, LCD, 1 line, 2 lines, etc. We have used Total Control Products OIT's both Smartscreen (CRT) and Quickpanels (LCD). Modicon Panelmates 1000 (LCD) 2000 (CRT), Spectrum Controls, these are some of the ones we have used that they have supplied Sy/Max Drivers for. We also have Panelviews, but have only used them on SLC500 Processors. Most OIT suppliers nowadays are getting away from or never supplied Sy/Max drivers. Hope this gets you started.

Steve Bailey

I'm not sure whether Square D called it anything other than the SyMax protocol. Whatever they call it, both Panel Mate and Total Control Products have the drivers for it.
If Square D ever had RTU capability, it was through a communications module.
The model 400 processors use a Sy/Max protocol, if you have room in the rack, NR&D makes a card that will do Modbus, Modbus plus and even Modbus
over Ethernet.

Rich Weekly, Branch Manager, Omaha / AE
Barr-Thorp Electric
4305 S. 94th Street
Omaha, NE 68127
[email protected] 402.331.3312

Ralph G. McDonald, P.E.


We still maintain a few old Sy/Max systems for a client. The com ports are RS-422/485. I have to use an RS-232 converter when I connect my laptop to the programming port. I work with Intellution, and they have drivers that work with Sy/Max 300/400/500 systems. Try I believe that Citect also has drivers for their HMI software.

Good Luck


Anthony Kerstens

Ken, Sy/Max is being phased out since it's purchase by your competitor, Schneider. Modicon PLC modules can be purchased to communicate on the Sy/Net network. Maybe there's a bridge MUX flavour that talks Sy/Net now, I'm not sure.

As for Metra, I have heard they are no longer, but that there is someone around milking the service contracts. I don't know who.

Anthony Kerstens P.Eng.

Hunter Farris

I have used the 422 protocol from these ports with the Total Control QuickPanel in the past. Have not had any problems in the past.

Hunter Farris

Jerry Miille

The protocol on both ports would be Sy/Max point to point protocol. You could use a protocol converter module such as the MARC Omnii-Comm to provide a Modbus connection to the Sy/Max ports.

Sy/Max processors talk Sy/Max protocol. HMI's that have been around for a while will have a driver for this. You need one that supports point-to-point Sy/Max protocol to connect directly to the processor.
Sy/Max processors do not support addressing. For multi-point apps. (ie., to make them addressable) you need a NIM (CRM-560) module in the rack.

If you want to talk Modbus, put a CRM-570 NIM in the rack, instead. This NIM can be configured to talk Modbus RTU up to 9600 baud. The address translation between Sy/Max memory and Modbus memory is straight-forward. The CRM-570 has only RS-485 ports on it. You can buy a programming cable from that will connect the OI (RS-232) to the NIM (RS-485) and is ready to run. Also suggest you buy a pre-fab cable from SQD to connect the 570 to this Sy/Max processor ( they have odd clip-on connector ).

If you get sticker-shock on a new CRM-570 price, there are some refurbs around.


Jay Kirsch
Macro Automatics
2985 E. Hillcrest Drive, Ste 101
Thousand Oaks, CA 91362
[email protected]

Cesar Garcia Cerveceria Polar de Oriente


Some time ago I make some test in a Sy/Max 400 using the programming port. This PLC used the Sy/Net protocol, if you need I can send you the complete description for this protocol (read and write register), but I think that you will need write a ASCII driver for communication with the panel.

If you need any other help let me know.

Cesar Garcia
Cerveceria Polar de Oriente, C.A.
Barcelona, Venezuela

Bill Szuminski

I would be careful about indicating a "phase-out" of any product. Unless you are the Sq D Product Manager you could be mistaken.
As a Sq D HTAD, I can buy and sell quite a lot of SYMAX equipment and as I'm sure you're aware, most major PLC manufacturers "support" their equipment far past the End of Life dates. WGS

Anthony Kerstens

Pardon me. Perhaps phase-out was the wrong word.
I should have said lack of new products in that
brand of PLC. Go to the Square D website and look at what they have for PLC's. It's Modicon.

Sorry if I mistook this for a phase-out.

Anthony Kerstens P.Eng.

Juan Manuel Noriega

Ken: I am not a very frequent user of this site, but searching for some information about symax i found your request. I have some experience in working with SY/Max, and the ports in the SCP 4XX are both RS422 you can send and recieve simple ASCII string by using the TREAD and TWRTE instruction in the processor to do serial comunications, the ASCII string can be up to 256 characters per block with block termination based either in character count or delimiter character.