Using Modbus with Indigo 202 - INDIGO201 - INDIGO202 - GMP252

GMP252 User Guide

Document code
English (United States)
Document type
User guide

Indigo 202 digital transmitters are designed for Modbus RTU (RS-485) communication. There are 2 groups of Modbus register addresses in use in Indigo 202: probe registers and Indigo registers. The probe registers are received from the connected probe, and are organized according to the probe's register map. Indigo registers include transmitter-specific information.

Received Modbus requests for register operations are treated in two different ways depending on the register address. Addresses above DFFFhex (that is, Indigo registers) are handled as normal requests. Lower addresses (that is, probe registers 0000hex ... DFFFhex) are passed to the measurement probe, and the response from the probe is again passed to original Modbus client. Indigo can also have a cache for commonly requested registers (Measurement registers).

The maximum response delay is 2 seconds (when data content needs to be fetched from the probe). The minimum delay between requests is 10 ms.

For more details on the information relayed within Indigo 202 (transmitter-specific) Modbus registers, see Indigo 202 Digital Transmitter User Guide.
Table 1. Indigo 202 Modbus Registers
Address Name Data Type
Probe registers (according to the connected probe's register map) 1
0000hex First measurement probe address
DFFFhex Last measurement probe address
Indigo registers
E000hex Status 16-bit
E001hex Notification and error bits 16-bit
E002hex Connected probe text [30]
E011hex Relay A status enum
E012hex Relay B status enum
1 See the connected probe's Modbus documentation for probe-specific register information