Vaisala Indigo 202 - Modbus; Modbus Overview

5. Modbus
5.1 Modbus Overview
Indigo 202 supports the Modbus RTU serial communication protocol (2-wire RS-485
in
terface).
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.
Table 3 Indigo 202 Modbus Registers
Address Name Data Type
Probe registers (according to the connected probe's register map)
1)
0000
he
x
First measurement probe address
DFFF
he
x
Last measurement probe address
Indigo registers
E000
he
x
Status 16-bit
E001
he
x
Notification and error bits 16-bit
E002
he
x
Connected probe text [30]
E011
he
x
Relay A status enum
E012
he
x
Relay B status enum
1) See the connected probe's Modbus documentation for probe-specific register information
Received Modbus requests for register operations are handled in two
dierent ways,
depending on whether the register is a probe register or an Indigo transmitter register.
Addresses above DFFF
hex
(that is, Indigo registers) are handled as normal requests. Lower
addresses (that is, probe registers 0000
hex
... DFFF
hex
) 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.
More Information
‣
Modbus Serial Communication Settings (page 34)
‣
Function Codes (page 65)
‣
Indigo Status Registers (page 65)
Chapter 5 – Modbus
39