Modbus overview - INDIGO200SERIES - INDIGO202

Indigo202 User Guide

Document code
Content type
Product description
Product description > Features
Product description > Functions
Document type
User guide

Indigo202 supports the Modbus RTU serial communication protocol (2-wire RS-485 interface).

There are 2 groups of Modbus register addresses in use in Indigo202: 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.

Table 1. Indigo202 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

Received Modbus requests for register operations are handled in two different ways, depending on whether the register is a probe register or an Indigo transmitter register. 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 the original Modbus client. Indigo can also have a cache for commonly requested registers (Measurement registers).

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

1 See the connected probe's Modbus documentation for probe-specific register information