Presentation of the Serial Link on Modicon M340 Processors.

General

The following processors have an integrated communication channel dedicated to serial communications, and enable communication via serial link:

BMX P34 1000
BMX P34 2000
BMX P34 2010
BMX P34 20102
BMX P34 2020

Serial Port Localization

The illustration below shows the localization of the serial port of the Modicon M340 processors:

These processors are composed of the following elements:

Address	Description
1	Processor status LEDs on the front
2	Integrated channel (channel 0) dedicated to the serial link.
3	Serial port identification ring (black)

Visual Diagnostic of Serial Communication

The status of the serial communication is indicated by a yellow SER COM LED on the front of these processors:

LED flashing: Serial communication is in progress.
LED off: Serial communication is not in progress.

Serial Port Connector Description

The illustration below shows the RJ45 serial port:

The RJ45 connector has eight pins. The pins used vary according to the physical link used.

The pins used by the serial link are:

Pin 1: RXD signal
Pin 2: TXD signal
Pin 3: RTS signal
Pin 6: CTS signal
Pin 8: Potential serial link grounding (0 V)

The pins used by the serial link are:

Pin 4: D1 signal
Pin 5: D0 signal

Pin 7 is used solely to supply power to human-machine interfaces or small devices via the serial link cable:

Pin 7: Serial link power supply: 5 VDC/190 mA

Detailed characteristics

DC characteristics:

Maximum stabilized power consumption: 190 mA,
Minimum voltage on CPU connector for 190 mA: 4.9 V,
Maximum voltage on CPU connector for 190 mA: 5.25 V,
Maximum voltage on CPU connector with no load: 5.5 V.

AC characteristics:

Capacitor charge: (on 5 V)
- Maximum 1 μF ceramic capacitor
- 10 μF tantalum
Pump charge startup: (on 5 V)
- 4 x 1 μF ceramic capacitor
- 2 x 10 μF tantalum

NOTE: The four-wire RS232, the two-wire RS485 and the two-wire RS485 with power supply all use the same female RJ45 connector. Only the signal cabling is different.

Electrical Line Characteristics

The RS232 and the RS485 lines are not isolated.

In case of non equipotential earth between connected equipments (cables equal or longer than 30 m), it is necessary to use a TWDXCAISO isolator module in RS485 mode.

The RS485 line polarisation is integrated into the and automatically enabled or disabled by the system according to the chosen in the screen:

Modbus master : The line polarisation is enabled.
Modbus slave : The line polarization is disabled.
Character mode : The line polarization is disabled.

The polarisation is not affected by dynamic protocol switching. The polarization resistors’ value is 560 ohms.

In RS232 mode, no polarization is required.

There is no built-in line termination.

Channel Specifications

The channel of these processors includes:

One non-isolated RS485 physical interface,
One non-isolated RS232 physical interface,
Modbus Serial (ASCII and RTU) and Character Mode communication types.

The link specifications for the two protocols are:

	Modbus Serial / RS485	Modbus Serial / RS232	Character Mode / RS485	Character Mode / RS232
Type	Master/Slave	Master/Slave	Half Duplex	Full Duplex
Flow	19200 bauds. Parameters can be set from 300 bauds to 38400 bauds.	19200 bauds. Parameters can be set from 300 bauds to 38400 bauds.	9600 bauds. Parameters can be set from 300 bauds to 38400 bauds.	9600 bauds. Parameters can be set from 300 bauds to 38400 bauds
Number of devices	32	32	_	_
Authorized slave addresses	1 to 247	1 to 247	_	_
Max. length of Bus without branching	1000 m (15 m with Branching)	15 m	1000 m (15 m with Branching)	15 m
Message Size	Modbus Serial: RTU: 256 bytes (252 bytes of data) ASCII: 513 bytes (2x252 bytes of data)	Modbus Serial: RTU: 256 bytes (252 bytes of data) ASCII: 513 bytes (2x252 bytes of data)	1024 bytes	1024 bytes
Utilities	Read words/bits. Write words/bits. Diagnostics.	Read words/bits. Write words/bits. Diagnostics.	Send character strings. Receive character strings.	Send character strings. Receive character strings.