Intesis
TM
INMBSMIT001I000
User’s Manual r22
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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4.4
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)
4.5
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
4.6
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 M
aster 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).