Allen-Bradley SLC 500 Manual page 97

The Push Button is a Momentary button with the tag variable assigned to RL1. One Numeric Data
Display is assigned to RL2 and the other to RL3. A Text display was assigned to RA1 for Invalid
Messages and another Text display was assigned to RA2 for Error Messages. The registers for Invalid
Messages and Error Messages are entered in Setup.
The Push Button is intended to send an ASCII string when it is pressed. The Data Display assigned to
RL2 is intended to poll the terminal for data. The Data Display assigned to RL3 is intended to display
data from an unsolicited command string sent from the controller. The terminal is able to send incorrect
command strings to check if the error messages and invalid messages appear in the text displays.
Protocol Setup
The Flex String Protocol dialog box used for the demo is shown below. The Invalid Msg Destination
register is assigned to RA1, which is the same tag used for the Invalid Message Text field. The Error
Msg Destination register is assigned to RA2, which is the same tag used for Error Message Text
display. The Reply Time Out was set to 3 seconds, which gives you plenty of time to click one of the
Function Keys in Terminal mode to send a character string. (The codes in the Function Keys are shown
later.)
The End of Packet Character is 13, which is a Carriage Return. This packet must be included in the
strings sent from the terminal.
ASCII Flex Protocol • • • • 265
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