I have an application whereby a barcode reader must sense a label and put the data in a table in a PLC. Using a decoder? (i think). This info is passed as ASCII? to the PLC
You are correct normally barcode readers that are connected to the PLC through serial means (RS232, DeviceNet, Profibus) will transfer the data to the PLC in ASCII format. I am not sure what PLC you are using but it doesn't really matter. You will either have to do some math to convert the ASCII to decimal format or if the PLC language you use supports it, use a ASCII to Decimal(integer)function block and put the converted value in a PLC register. Next have your MES or SCADA interface reference to that register for the Barcode number.
What is MES? Manufacturing Execution System...the control layer above your SCADA (level II) system that interfaces with the business systems, usually for part tracking.
I am currently adding this same functionality to a group of A-B SLC 5/05 (ethernet) PLC's. I am using the 1746-BASIC-T module for the ASCII interface, a handheld scanner with RF communications and wand emulation (important) and Parijat ActiveX control for the PC to interface with all the PLC's in order to get the data into a MS SQLServer database. It would have been possible to use the DF-1 port, but the BASIC module gives me better range checking and other capabilities that make it worth the expense ($1300 List).
That depends on your processor configuration and what ports are available. If you have a spare DF1 port, you can use that but functionality will be limited. I recommend the 1746-BAS-T ($1300 list) or the 1746-BASC ($1100 list), the only difference between them is processing speed. For the BASIC modules I would also recommend getting the BASIC programming software 1747-PBAS ($800 list) but you could use terminal emulation.