Instructions

Intesis
®
INMBSMIT001I000
User’s Manual r2.4 EN
© HMS Industrial Networks S.L.U - All rights reserved
This information is subject to change without notice
URL https://www.intesis.com
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3.4 Implemented Functions
INMBSMIT001I000 implements the following standard Modbus functions:
▪ 3: Read Holding Registers
▪ 4: Read Input Registers
▪ 6: Write Single Register
▪ 16: Write Multiple Registers (Despite this function is allowed, the interface does not
allow to write operations on more than 1 register with the same request, this means that
length field should be always be 1 when this function is being used in case of writing)
3.5 Device LED indicator
The device includes a LED indicator to show all the possible operational states. In the following
table, there is a description for each indication.
Device status
LED indication
ON / OFF Period
Description
On power-up
LED pulse
ON for 5 seconds / OFF after
Device reset / power-up
During normal
operation
LED flashing
200ms ON / 2s OFF
Device correctly configured and
working
During normal
operation
LED OFF
OFF continuously
No Modbus Slave address
configured
During normal
operation
LED blinking
200ms ON / 200ms OFF
Communication Error with the AC
unit
3.6 EIA-485 bus. Termination resistors and Fail-Safe Biasing
mechanism
EIA-485 bus requires a 120Ω terminator resistor at each end of the bus to avoid signal
reflections.
In order to prevent fail status detected by the receivers, which are “listening” the bus, when all
the transmitters’ outputs are in three-state (high impedance), it is also required a fail-safe
biasing mechanism. This mechanism provides a safe status (a correct voltage level) in the bus
when all the transmitters’ outputs are in three-state. This mechanism must be supplied by the
Modbus master.
The INMBSMIT001I000 device includes an on-board terminator resistor of 120Ω that can be
connected to the EIA-485 bus by using DIP-switch SW4.
Some Modbus RTU EIA-485 Master devices can provide also internal 120Ω terminator resistor
and/or fail-safe biasing mechanism (check the technical documentation of the Master device
connected to the EIA-485 network in each case).