Device Definition

To change the definition of a device, select Device definition in the Overview view.
When you add the module in the project for the first time, Device Definition dialog shows only Overview view with Channel 0 set to Disabled by default. Depending on what you choose for the parameter Channel 0, you can have additional parameters.
If you set Channel 0 to Modbus Master, you can see Channel 0 – Modbus Master view. For more information, see Channel 0 – Modbus Master View.
If you set Channel 0 in Overview view to Modbus Slave, you can see Channel 0 – Modbus Slave view. For more information, see Channel 0 – Modbus Slave View.

Overview View

Use Overview view in the Device Definition dialog to define a device or change the device definition.
Device Definition Dialog – Overview View
Overview view includes these parameters:
Device Definition Dialog – Overview View Parameters
Parameter
Definition
Available Choices
Device Type
Displays the device catalog number and type.
Device-specific
Name
Enter an IEC 61131 compliant device name.
If an invalid character is entered in this field, or if the name exceeds 40 characters, the software ignores the character.
All valid values
Description
Enter the description of the device.
All valid values
Slot
Specify the slot number where the device resides. Only slots between 1 and the maximum number of I/O devices are valid depending on the platform
When the device is created, the slot number defaults to the first available slot position.
When the controller is changed to one supporting a smaller maximum I/O count, the current slot value may no longer be valid.
1...32
Series
Specifies the series of the device.
Device-specific
Revision
Specifies the major and minor revisions of the device. The valid range for minor revision is from 1...255.
Device-specific
Electronic Keying
Defines the electronic keying used for the device. Electronic keying compares the device defined in the project to the installed device. If keying fails, a fault occurs.
For detailed information on Electronic keying, see Electronic Keying in Logix 5000 Control Systems Application Technique, publication LOGIX-AT001.
  • Exact Match
  • Compatible Module
  • Disable Keying
ATTENTION:
Be extremely cautious when using Disable Keying; if used incorrectly, this option can lead to personal injury or death, property damage, or economic loss.
We strongly suggest that you do not use Disable Keying.
If you use Disable Keying, you must take full responsibility for understanding whether the device being used can fulfill the functional requirements of the application.
Connection
Specify the type of data transferred between the device and controller.
Data (default)
Channel 0
Specifies the protocol used by the channel to transmit data to and receive data from a Serial device.
  • Disabled
  • Generic ASCII
  • Modbus Master
  • Modbus Slave
For more information, see Table 2.
Communication Mode Definitions
Communication Mode
Definition
Disabled
The channel is unused and no physical connection is enabled between the controller and the serial module.
Generic ASCII
A general mode of serial communication where you can define any user data to be transmitted or received in the communication.
Modbus Master
The device sends Modbus queries or write commands to the slave devices connected to it.
Modbus Slave
The device operates as a slave to an external master and waits for commands from the Master.

Channel 0 – Modbus Master View

The Modbus Master view allows you to define the Modbus Master device.
Channel 0 – Modbus Master View Example
Modbus Master view includes these parameters:
Modbus Master Command List Parameters
Parameter
Definition
Available Choices
Command
Displays the index of the command being configured.
0...49
Communication Method
Specifies the communication method for the command.
TIP: Parameters are unavailable when the communication method is disabled.
  • Disabled (default)
  • Continuous – Modbus command message is transmitted continuously.
  • Conditional – Modbus command message is transmitted when the consume Modbus command data is changed.
    Some Function Code options are not available for the Conditional communication method.
Data Type
Specifies the data type for the command.
  • BOOL
  • INT (default)
  • REAL
Function Code
Specifies the function of the command.
See Table 4 for the description of each function code choice.
Specifies the function of the command. Valid values are depend on the Data Type.
If Data Type is BOOL:
  • Read Coils
  • Read Discrete Inputs
  • Write Single Coil
  • Write Multiple Coils
If Data Type is INT:
  • Read Holding Registers
  • Read Input Registers
  • Write Single Register
  • Write Multiple Registers
If Data Type is REAL:
  • Read Holding Registers
  • Read Input Registers
  • Write Multiple Registers
Slave
Specifies the node address of the Modbus Slave device.
Valid addresses of a specific Modbus Slave device are 1...247. For broadcast command, set the slave to 0. Broadcast command can only be write commands.
Register Start Address
Specifies the start address of the registers being read or written.
0...65,535
Data Count
Specifies the number of data of the Data Type being read or written.
If REAL is used, each data uses 2 Registers.
The number of consecutive registers read/written are as follows:
  • For BOOL: Equal to Data Count
  • For INT: Equal to Data Count
  • For REAL: Equal to (Data Count * 2)
The end address caused by Data Count must not exceed the max address of 65,535. The end address is calculated as (Register Start Address + Number of registers - 1).
The valid data length values depend on the Data Type and the Function Code.
Function Code
Valid Value
Read Coils
1...2000
Read Discrete Inputs
1...2000
Read Holding Registers
  • For INT Data Type, 1...125
  • For REAL Data Type, 1...62
Read Input Registers
  • For the INT Data Type, 1...125
  • For the REAL Data Type, 1...62
Write Single Coil
Not Applicable
Write Single Register
Not Applicable
Write Multiple Coils
1...1968
Write Multiple Registers
  • For the INT Data Type, 1...123
  • For the REAL Data Type, 1...61
Poll Interval
Specifies the number of seconds between each time the command is executed when it is in Continuous mode.
For example, if the Poll Interval is set at 10, the Modbus Master waits 10 seconds before executing the command again. When the Poll Interval is set at 0, the Modbus Master repeats transmitting the command as fast as possible.
TIP: This parameter is unavailable when the Communication Method is Conditional.
0...32,767
Swap Mode
Specifies the arrangement of every 4 bytes of data received from or transmitted to the Modbus Slave.
  • No Change (ABCD → ABCD)
  • Word Swap (ABCD → CDAB)
  • Byte Swap (ABCD → BADC)
  • Word and Byte Swap (ABCD → DCBA)
TIP: A, B, C, and D represent four adjacent bytes in the received/transmitted data.
Fault Enable
Determines whether to overwrite the received data with a Fault Value if the read command fails.
Select the checkbox to overwrite the received data with the Fault Value.
TIP: This parameter is unavailable when the Function Code is a write command.
–
Fault Value
Specifies the value to replace the received data if the read command fails.
–
Connection 1/Connection 2
Command communication uses Connection 1 by default.
If a command data size exceeds the remaining amount of data available for Connection 1, the command uses Connection 2 instead.
–
Input
Shows the amount of read data remaining for that connection.
–
Output
Shows the amount of write data remaining for that connection.
–
Description of Function Codes
Data Type
Function Code
Description
BOOL
Read Coils (Function Code 01)
Reads 1...2000 contiguous status of Coils in a slave device.
Read Discrete Inputs (Function Code 02)
Reads 1...2000 contiguous status of Discrete Inputs in a slave device.
Write Single Coil (Function Code 05)
Writes a single output to either ON or OFF in a slave device.
Write Multiple Coils (Function Code 15)
Writes 1...1968 contiguous output to either ON or OFF in a slave device.
INT
Read Holding Registers (Function Code 03)
Reads 1...125 contiguous block of INT Holding Registers in a slave device.
Read Input Registers (Function Code 04)
Reads 1...125 contiguous block of INT Input Registers in a slave device.
Write Single Register (Function Code 06)
Writes a single Holding Register in a slave device.
Write Multiple Registers (Function Code 16)
Writes 1...123 contiguous block of INT Holding Registers in a slave device.
REAL
Read Holding Registers (Function Code 03)
Reads 1...62 contiguous block of REAL Holding Registers in a slave device.
Read Input Registers (Function Code 04)
Reads 1...62 contiguous block of REAL Input Registers in a slave device.
Write Multiple Registers (Function Code 16)
Writes 1...61 contiguous block of REAL Holding Registers in a slave device.
Master Command List Limitations
Master command list limitations are:
  • A maximum of 50 commands can be created. The commands are subject to available connection memory.
  • Each Modbus Master supports up to two data connections.
  • Connection 1 supports a maximum of 464 bytes of read data and 476 bytes of write data.
  • Connection 2 supports a maximum of 472 bytes of read data and 488 bytes of write data.
  • Each command uses:
    • 2 bytes of input data per holding register or input register read.
    • 1 byte of input data per every 1…8 coils or discrete inputs read.
    • 2 bytes of output data per holding register written.
    • 1 byte of output data per every 1…8 coils written.
  • An error message appears when connection memory is exceeded.
Master Command Memory Usage
The following are the examples of master command memory usage:
  • Maximum single connection configuration for registers:
    • 223 words * 2 bytes/word read = 446 input bytes
    • 241 words * 2 bytes/word written = 482 output bytes
  • Maximum single connection configuration for coils:
    • 3576 bits / 8 bits/byte read = 447 input bytes
    • 3856 bits / 8 bits/byte written = 482 output bytes

Channel 0 – Modbus Slave View

The Modbus Slave view allows you to define the Modbus Slave device.
Channel 0 – Modbus Slave View Example
Modbus Slave view includes these parameters:
Modbus Slave Data Mapping Parameters
Parameter
Definition
Available Choices
Register Mapping Number
Displays the Register Mapping Number.
0...29
Register Type
Specifies the type of register.
TIP: Parameters are unavailable when the register type is disabled.
  • Disabled (default)
  • Coils
  • Discrete inputs
  • Input registers
  • Holding registers
Data Type
Specifies the data type for the register.
Available options are based on the Register Type you choose.
For Coils and Discrete Inputs, available option is:
  • BOOL
For Holding Registers and Input Registers, available options are:
  • INT
  • REAL
Register Start Address
Specifies the start address of the register.
0...65,535
Data Count
Specifies the number of data of the Data Type.
Valid values are depend on the Data Type:
  • BOOL: 1...128
  • INT: 1...100
  • REAL: 1...50
The number of consecutive registers read/written are as follows:
  • For BOOL: Equal to Data Count
  • For INT: Equal to Data Count
  • For REAL: Equal to (Data Count * 2)
For any two mappings with the same register type, their register ranges must not overlap. The register range for each mapping spans from the Register Start Address to the end address of the mapping. The end address is calculated as (Register Start Address + Number of registers - 1).
The end address of each mapping must not exceed the max address of 65,535.
Buffer Index
Specifies the buffer index of the register buffers in input and/or output tags. These tags are HoldingRegister[y], Coil[z], InputRegister[y], and DiscreteInput[z] where "y" and "z" are Buffer Index.
  • 0...15 for Coils/Discrete Inputs
  • 0...99 for Holding/Input Registers
The number of consecutive buffers occupied by this register mapping are as follows:
  • For BOOL: Equal to the round-up of (Data Count / 8)
  • For INT: Euqal to Data Count
  • For REAL: Equal to (Data Count * 2)
For any two register mappings with the same register type, their buffer ranges must not overlap. The buffer range spans from Buffer Index to the end buffer index caused by Data Count. The end buffer index is calculated as (Buffer Index + Number of buffers - 1).
The end buffer index of each mapping must not exceed the valid range of Buffer Index defined above.
Buffer Index Error Example
Modbus Slave Address Table Limits
Up to 30 data point ranges can be created in the Module Slave address table, subject to available memory:
  • 200 byte maximum of Holding Registers (up to 100 INTs or 50 REALs)
  • 200 byte maximum of Input Registers (up to 100 INTs or 50 REALs)
  • Up to 128 Coils (Data Indexes 0…15 at 8-bit boundaries)
  • Up to 128 Discrete inputs (Data Indexes 0…15 at 8-bit boundaries)
Modbus Slave Data Mapping Example
Modbus Slave Data Mapping Example
The data represented in Figure 5 can be interpreted from the module tags as follows:
  • v:2:O1.Slave.HoldingRegister[0…2] = 400003…400005
  • v:2:O1.Slave.HoldingRegister[3…9] = 432000…432006
  • v:2:O1.Slave.HoldingRegister[10…99] = 400999…410088
  • v:2:O1.Slave.Coil[0].0…0.7 = 000000…000007
  • v:2:O1.Slave.Coil[1].0 = 000010
  • v:2:O1.Slave.Coil[2].0…[4].0 = 0320000…032016
  • v:2:O1.Slave.Coil[5].0…[15].7 = 000999…001086
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