I have need of an HMI-PLC unit with a serial (RS-232) port and possibly a USB port (for exporting collected data records) that can communicate as follows:
115Kb data rate, * bits, Odd parity, 1 stop bit, <STX> start, <ETX> end, followed by <bcc> checksum code at tail end which consists of an XOR 8-bit value of all characters preceding it (including the <STX> and <ETX> characters.
I realize I can create the string within the ladder code prior to TX, but the protocol itself, adding the <bcc> at the end, is sometimes problematic with HMIs, as not many of them support this functionality.
I have used the Unitronics with the built-on HMI screen before, reading fast barcode scanners, worked well. But, that was a canned protocol, no check code, no variable-length strings, etc., so ths one is tougher.