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Rosemount 5300 Series with HART® to Modbus® Converter
May 2016
Reference Manual
00809-0100-4530, Rev DD
397
Rosemount 5300 Series with HART® to Modbus® Converter
Assign Heartbeat to one of the transmitter variables (SV, TV, or QV). Heartbeat is increased
by one for each measurement cycle in the device (until it eventually starts over at zero
again).
In case this value is not updated, it means that the communication link is broken.
J.10
Common Modbus host configuration
When using Modbus RTU or Modbus ASCII, the registers to receive status and variables
must be configured in the host system.
The transmission of single-precision (4 bytes) IEEE 754 floating point numbers can be
rearranged in different byte orders specified by the Floating Point Format Code. The format
code information, stated for each Remote Terminal Unit (RTU) respectively, specifies which
registers to poll from the Rosemount 5300 Series Transmitter in order for the RTU to
correctly interpret floating point numbers. The byte transmission order for each format
code is demonstrated in
below.
Table J-12. Byte Transmission Order is Specified by the Floating Point Format Code
Note
Some Modbus hosts cannot read the information described here using Input Registers
(Modbus function code 4). The Input Register information can also be read using Holding
Register (Function code 3). In this case, Input Register 5000 is used as Holding
Register number.
Between host system and device, it is recommended to use 60 seconds or less between
polls, and three retries.
J.10.1
Input registers
The register area starting with 1300 can be configured to have any of the four format codes.
The configuration is done by setting FloatingPointFormatCode register (holding register
3000) to 0-3, as shown in
. This configuration can be done with the Rosemount
Radar Master program.
Note
Depending on the slave number the Rosemount 5300 Series Transmitter is using, different
registers must be used with the default slave number being 1. Slave number is determined
by the HART address.
Format Code
Byte transmission order
Description
0
[AB] [CD]
Straight word order, most significant byte first
1
[CD] [AB]
Inverse word order, most significant byte first
2
[DC] [BA]
Inverse word order, least significant byte first
3
[BA] [DC]
Straight word order, least significant byte first