AMB-8I

AMB-8I is a digital input extender with high voltage range from 60V AC up to 500V AC. Input also support DC voltage in same voltage range. The power supply range is 8 to 36V and accept DC or AC voltage.

General information

Download technical specification Technical Specification

Configuration manual

Features


Protocol Description

MODBUS Protocol is a messaging structure, widely used to establish master-slave communication between intelligent devices. A MODBUS message sent from a master to a slave contains the address of the slave, the 'command' (e.g. 'read register' or 'write register'), the data, and a check sum (LRC or CRC).
Since Modbus protocol is just a messaging structure, it is independent of the underlying physical layer. In AMB-4I-4O is implemented using RS485 interface.

Modbus RTU Framing

The AMB-4I-4O module supports standard RTU Modbus protocol for getting the input status and setting/getting the relays status. RTU Modbus Protocol frame is illustrated below:

Start Address Function Data
RC Check End
≥ 3.5 Char 4 Bits

8 Bits

N*8 Bits 16 Bits ≥ 3.5 Char
Modbus Serial Port Parameter
Parameter Option/range
Baudrate 9600 – 128000 configurable
ata bit 8
Parity None
Stop bit 1
ID Configuration of Modbus Card

User can set the slave ID address using 8 Bit DIP switch found on board. This allow 0 to 255 different IDs to be set. The number below the switches are added together and the result will be identifier of the device slave ID.
To set the slave ID 125, you need to turn ON switch 1,3,4,5,6,7 on DIP switch and OFF the others (In this, convert slave ID number 125 into 8bit binary form – 01111101, turn ON DIP switch 1,3,4,5,6,7 and turn OFF DIP switch 2,8) and so on…. 

AMB-4I-4O-DIP.png

Baudrate Configuration

User can set the baudrate using 4 Bit DIP switch found on board. To set baudrate, first turn off power supply of card. This allows to set baudrate between 2400bps to 128000bps as shown below table.

Baudrate SW1 SW2 SW3 SW4
9600 OFF OFF OFF OFF
2400 ON OFF OFF OFF
4800 OFF ON OFF OFF
14400 OFF OFF ON OFF
19200 OFF OFF OFF ON
28800 ON ON OFF OFF
38400 OFF ON ON OFF
57600 OFF OFF ON ON
115200 ON OFF OFF ON
128000 ON ON ON ON

Modbus RTU Commands

The following commands (functions) were implemented in the Modbus RTU AMB-4I-4O.

Coils are mapped to outputs and discrete inputs are mapped to inputs. Coils read/write output status and discrete inputs read Input status. There are 4 inputs for reading-input 0 to input 3 which refer to input 1 to input 4 and coil 0 to coil 3 which refer to output 1 to output 4.

Note: For all below example, consider slave address – 0x01 will change with 8bit DIP switch.


01 (01 hex) Function Code – Read Coils

Read Coils command is requesting the ON/OFF status of coils. Read Coils command will return individual current outputs status. Also Read Coils Command will return sequentially outputs current status. 

Example of how to read output status are given below:

REQUEST FRAME –

01 01 0000 0008 3DCC
01 – The Slave Address (01 hex = 01)
01 – The Function Code 
0000 – The Data Address of first coil to read (0000hex = coil 0)
0008 – The total number of inputs requested (0008hex = 8 inputs)
3DCC – The CRC for error checking

RESPONSE FRAME – 

01 01 01 C9 91DE
01 – The Slave Address (01 hex = 01)
01 – The Function Code 
01 – The number of data bytes to follow (8 inputs / 8 bits per byte = 1 byte)
C9 – Input 0 to 7(Inputs), C9 hex = 1100 1001 (0 – ON, 1 – OFF)
91DE – The CRC for error checking


Modbus Exception Codes

Exception responses from either the master or a slave can result from data processing errors.
One of the following events can occur after a request from the master:

Exception Frame:

Sn. Definition Description
1 Slave Address The Slave Address of requested slave
2 Exception Function Code Requested Function Code + 128 (0x80)
3 Exception Code See in next table
4 CRC check The CRC for error checking

Exception Codes:

Exception Code Name Description
0X01 Illegal Function Code The function code received in the request is not an allowable action for the slave. This may be because the function code was not implemented in the unit selected. 
0x02 Illegal Data Address The data address received in the request is not an allowable address for the slave.
0x03 Illegal Data Value A value contained in the request data field is not an allowable value for the slave.  This indicates a fault in the structure of remainder of a complex request, such as that the implied length is incorrect. 

Safety information

Operating environment

Use in inappropriate conditions may damage the device or shorten its life.


Electrical and power supply safety

Only a person with qualification and appropriate knowledge should install the device.


Malfunctioning and damaged device

Radio frequency exposure

This device has been designed and manufactured not to exceed radio frequency energy emission limits set by regulatory agencies. To comply with RF exposure guidelines, the device must be used at least 20 cm away from a person's body. Failure to follow these instructions may result in exceeding the applicable RF exposure limits. This only applies to models with a built-in LTE modem.


What to do and what not to do