Allen-Bradley MicroLogix 1200 Reference Manual page 280

20-12 ASCII Instructions
Publication 1762-RM001C-EN-P
to be sent or, send data on a time interval. If sent on a time interval, use
an interval of 0.5 second or greater.
Do not continuously generate streams of ASCII data out of
IMPORTANT
a communications port. If ASCII write instructions execute
continuously, you may not be able to re-establish
communications with RSLogix 500 when the controller is
placed into the RUN mode.
This instruction executes on a true rung. Once started, if the rung goes
false, the instruction continues to completion. If you want to repeat this
instruction, the rung must transition from false-to-true.
When using this instruction you can also perform in-line indirection. See
page 20-29 for more information.
Entering Parameters
Enter the following parameters when programming this instruction:
• Channel is the number of the RS-232 port, Channel 0. (For the
1764-LRP only, you can select either Channel 0 or Channel 1).
• Source is the string element you want to write.
• Control is the control data file. See page 20-6.
• String Length (.LEN) is the number of characters you want to write
from the source string (0 to 82). If you enter a 0, the entire string is
written. This is word 1 in the control data file.
• Characters Sent (.POS) is the number of characters that the controller
sends to an external device. This is word 2 in the control data file.
Characters Sent (.POS) is updated after all characters have been
transmitted.
The valid range for .POS is from 0 to 82. The number of characters
sent to the destination may be smaller or greater than the specified
String Length (.LEN) as described below:
– Characters Sent (.POS) may be smaller than String Length (.LEN) if
the length of the string sent is less than what was specified in the
String Length (.LEN) field.
– Characters Sent (.POS) can be greater than the String Length
(.LEN) if inserted values from in-line indirection are used. If the
String Length (.LEN) is greater than 82, the string written to the
destination is truncated to 82 characters.
• Error displays the hexadecimal error code that indicates why the ER
bit was set in the control data file. See page 20-30 for error code
descriptions.