Allen-Bradley micrologix 1500, User Manual

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Publication 1764-UM001A-US-P
E-18 Understanding Communication Protocols
ASCII Protocol
(MicroLogix 1500
1764-LSP and 1764-LRP
Series B Processors
only)
ASCII protocol provides connection to other ASCII devices, such as bar code
readers, weigh scales, serial printers, and other intelligent devices.
You can use ASCII protocol by configuring the RS-232 port, channel 0 for ASCII
driver (
For the 1764-LRP only, you can select either Channel 0 or Channel 1 ). Refer to
the MicroLogix 1200 and MicroLogix 1500 Programmable Controllers Instruction Set
Reference Manual , publication 1762-RM001B-US-P for detailed configuration
information.
When the driver is set to ASCII, the following parameters can be changed:
Table E.6 ASCII Channel Configuration Parameters
Parameter Description Programming
Software Default
Baud Rate Toggles between the communication rate of 300, 600, 1200, 2400, 4800, 9600, 19.2K, and 38.4K. 1200
Parity Toggles between None, Odd, and Even. None
Termination 1 Specifies the first termination character. The termination character defines the one or two character
sequence used to specify the end of an ASCII line received. Setting the first ASCII termination
character to undefined (\ff) indicates no ASCII receiver line termination is used.
\d
Termination 2 Specifies the second termination character. The termination character defines the one or two
character sequence used to specify the end of an ASCII line received. Setting the second ASCII
Termination character to undefined (\ff) and the first ASCII Termination character to a defined value
(\d) indicates a single character termination sequence.
\ff
Control Line Toggles between No Handshaking, Half-Duplex Modem, and Full-Duplex Modem No Handshaking
Delete Mode The Delete Mode allows you to select the mode of the “delete” character. Toggles between Ignore,
CRT, and Printer.
Delete Mode affects the characters echoed back to the remote device. When Delete Mode is enabled,
the previous character is removed from the receive buffer.
•
In CRT mode, when a delete character is encountered, the controller echos three characters to the
device: backspace, space, and backspace. This erases the previous character on the terminal.
•
In Printer Mode, when a delete character is encountered, the controller echos the slash character,
then the deleted character.
Enable the Echo parameter to use Delete Mode.
Ignore
Echo When Echo Mode is enabled, all of the characters received are echoed back to the remote device. This
allows you to view characters on a terminal connected to the controller. Toggles between Enabled and
Disabled. Disabled
XON/XOFF Allows you to Enable or Disable XON/ XOFF software handshaking. XON/XOFF software handshaking
involves the XON and XOFF control characters in the ASCII character set.
When the receiver receives the XOFF character, the transmitter stops transmitting until the receiver
receives the XON character. If the receiver does not receive an XON character after 60 seconds, the
transmitter automatically resumes sending characters.
Also, when the receive buffer is more than 80% full, an XOFF character is sent to the remote device to
pause the transmission. Then, when the receive buffer drops to less than 80% full, an XON character
is sent to the remote device to resume the transmission. Disabled
RTS Off Delay
(x20 ms) Allows you to select the delay between when a transmission is ended and when RTS is dropped.
Specify the RTS Off Delay value in increments of 20 ms. Valid range is 0 to 65535. 0
RTS Send
Delay (x20 ms) Allows you to select the delay between when RTS is raised and the transmission is initiated. Specify
the RTS Send Delay value in increments of 20 ms. Valid range is 0 to 65535. 0