Rockwell Automation 2711P Creating Modbus Applications - Manual (Page 76)

Publication 2711P-UM002B-EN-P - March 2007
76 Modbus Unsolicited Serial Address Definitions
String Support
The Modbus model supports reading and writing holding register
memory as an ASCII string. When using holding registers for string
data, each register will contain two bytes of ASCII data. The order of
the ASCII data within a given register can be selected when the string
is defined. The length of the string can be 2 to 240 bytes and is
entered in place of a bit number. The length must be entered as an
even number. The byte order is specified by appending either an H or
L to the address.
String Example:
To address a string starting at 40200 with a length of 100 bytes and
HiLo byte order enter:
40200.100H