I need some explaination on how these 2 channels (0 and 1 ) in SLC 5/04 are different (physically and thereotically). Another thing is when I go in "Channel Configuration", there are two channel 0 ,"Channel 0-System" and "Channel 0-User" , and I don't know when one is used and when it is not. Thank y'all

channel 1 on a 5/04 is the DH+ port on the front face of the card. 5/03s have a RS485/DH485 port and 5/05s have an ethernet port.

Channel 0 on the 5/03, 5/04, and 5/05 are RS232 ports and can be placed in either USER or SYSTEM mode.

In SYSTEM mode, port 0 supports the protocol that they are configured for. The default protocol is DF1 but can also support DH485.

In USER mode, port 0 becomes available for ASCII communication by the ladder program. There exists some instructions that can be executed to read and write to the serial port and some commands to control the handshaking lines if hardware handshaking is selected.

The newer Micrologix processors have added MODBUS and MODBUS RTU as allowable protocols.

in Channel 0, how can you switch between user mode or system mode ?

Greetings Mikey431,

everything posted by jstolaruk was correct ... but just to nail it down in basic “rule of thumb” ideas, try looking at Channel 0 this way:

in “System” mode, the port is used for programming the SLC ...

in “User” mode, the port is set up for use with things like printers, barcode scanners, modems, etc. ...

there’s more to it than that of course, but I’ve got a hunch that this is the type of information you were asking for ...

as for how to change between System and User mode, you might find this previous post interesting ... in particular, notice the neat idea suggested by Ken Roach ... normally the switch is made by a programmer going online with the processor (through either Channel 1 or through Channel 0 in the System mode) and then making the change in the Channel Configuration feature ...