Lenze RS-485 module - Manual (Page 6)

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Technical Data
3.3 Configuration
Drive 94 supports Modbus communication protocol through its RS485 optional card.
The following Communication parameters are available:
RS485 configuration – If the value of this parameter is ‘Modbus slave’ the modbus slave protocol is
enabled on the RS485 port. If the value is ‘Normal’ the RS485 works in PPP mode.
Modbus baud rate – the RS485 baud rate in modbus mode. Note that modbus requires 2 stop bits
and no parity.
Modbus reply delay – The delay introduced after receiving modbus request and before sending a
reply. Note that this delay will always be >= 3.5 characters as required by the modbus specification.
Some modbus master devices are slow and an increase of the ‘Modbus reply delay’ value might be
required to successfully work with these devices.
Each device in the Modbus network must have its own unique network address.
The ‘Addr’ submenu on the drive display and the front panel buttons can be used to set the Modbus
network address.
Drive 94 is Modbus slave devices in a single master multiple (or one) slaves network.
(Sometimes Slave devices are named servers because they wait for requests.)
Drive 94 communicates on the other end with Modbus Master.
Most Terminals can be configured as Masters with a Modbus Generic driver.
3.4 Supported Modbus features
Drive 94 uses the Modbus protocol delay of 3.5 characters time between packets to determine the
end of packet.
The following ModBus functions are supported:
• 01 (0x01) Read Coils
• 02 (0x02) Read Discrete Inputs
• 03 (0x03) Read Holding Registers
• 04 (0x04) Read Input Registers
• 05 (0x05) Write Single Coil
• 06 (0x06) Write Single Register
• 15 (0x0F) Write Multiple Coils
• 16 (0x10) Write Multiple Registers
When the drive receives ModBus function it executes it and replies with Normal message, Exception
Message or No message as described by the Modbus Application protocol Specification V1.1.
Modbus broadcast address is supported by the drive 94 also. In this case after receiving correct
Modbus request the drive executes it but does not send any reply back.
The DWORD (double word) and FLOAT numbers are send with the LOW WORD FIRST convention
by the 94 drive.
Note that some Terminals may have to be configured appropriately in order to accept such a WORD
order.