Chapter 9. Communication; Modbus Communication; Modbus Register Map - GE TransPort PT900 User Manual

Chapter 9. Communication

9.1 Modbus Communication

In general, the PT900 flow meter follows the standard Modbus communications
protocol defined by the reference MODBUS APPLICATION PROTOCOL
SPECIFICATION V1.1b
this reference as a guide, the user may use any Modbus master to communicate
with the flow meter.
Two limitations of this implementation are:
•
The PT900 supports only four of the standard function codes. These are
Read Holding Registers (0x03), Read Input Registers (0x04), Write
Multiple Registers (0x10) and Read File Record (0x14).
•
The flow meter needs a 15 ms gap between Modbus requests. The prime
objective of the flow meter is to measure flow rate and drive the output, so
the Modbus server has a low priority.

9.2 Modbus Register Map

Table 17 below lists the complete Modbus register map for the PT900.
Register Register
(in Hex) (in Dec.)
100 100 256
108 264
118 280
120 288
128 296
130 304
138 312
140 320
148 328
150 336
158 344
300 300 768
304 772
308 776
500 500 1280
502 1282
®
TransPort PT900 User's Manual
. This specification is available at
Table 17: Modbus Register Map
Access Description
Level
User Product Short Tag
User Product Long Tag
User eAI1Label
User eAI2Label
User eLogName
User Product Electronical serial number
User Product fixture serial number
User Product transducer1 serial number
User Product transducer2 serial number
User Product transducer3 serial number
User Product transducer4 serial number
RO Main Hardware version
RO Option Hardware version
RO Main Software version
User Global Unit group 1 for Actual Volumetric
User Global Unit group 2 for Day
Chapter 9. Communication
www.modbus.org
RO/ Format
RW
RW CHAR * 16
RW CHAR * 32
RW CHAR * 16
RW CHAR * 16
RW CHAR * 16
RW CHAR * 16
RW CHAR * 16
RW CHAR * 16
RW CHAR * 16
RW CHAR * 16
RW CHAR * 16
RO CHAR * 8
RO CHAR * 8
RO CHAR * 8
RW INT32
RW INT32
. With
141