Rockwell Automation 1758-RTU202 DataSite Software User Manual FRN 1.2 - Manual (Page 267)

267 Publication 1758-UM002D-EN-P - October 2010
Chapter
4
Extension Modbus Protocol for DataSite
Controllers (1758-FLO)
This chapter describes communication with a SCADA system using the
Extension Modbus protocol. The Extension Modbus protocol is fully
compatible with standard Modbus. All data interchanges, including flow
history data, are accomplished using the Extension Modbus protocol.
Modbus Register Definition The DataSite controller uses the Modbus address to share data between C
programs and communication protocols. The section describes the Modbus
registers used in the DataSite controller, including general purpose registers
and user-assigned registers.
Data formats
Data Type Number of Registers
Required Description
u_char 1 Unsigned integer in the range 0…255.
u_short 1 Unsigned integer in the range 0…65535.
u_int 2 Unsigned integer in the range
0…4294967295.
float 2 IEEE single precision floating-point number.
Data attributes
Attribute Description
RW Read/write
RO Read-only
W Write
R Read