TK506 - RS-485 Isolator for COM1 (AC500-eCo)

• Isolated side: 5-pole terminal
• AC500-eCo-side: SUB-D 9-pin, male
• Length 0.6 m

1	9-pole Sub-D terminal, male, RS-485
2	DIN rail mounting spring
3	Holes for mounting with 2x M4 screws
4	5-pole terminal, screw-type, RS-485

Intended Purpose

The RS485 Isolator TK506 for COM1 of processor module modules PM55x and PM56x allows longer cable length for serial communication. The product can be used for the communication protocols Modbus RTU or CS31 System Bus.

Note

The RS-485 Isolator TK506 can only be used with PM55x and PM56x processor modules with version index A3 and higher. You can find this index on the type label on the right side of the processor module (see photo of type label below).

The isolator provides galvanic isolation of the RS-485 communication signals. It is supplied via the 3.3 V output of the COM1 interface of the Processor Module. The isolator automatically detects and follows serial data flow direction changes. It is adapted to communication speeds up to 187.5 kBaud.

Electrical Connection: Interface

Pin No.	Signal	Description
1	Terminator P	Terminator positive
2	RxD/TxD-P	Receive/transmit positive
3	RxD/TxD-N	Receive/transmit negative
4	Terminator N	Terminator negative
5	FE	Functional earth (internally connected to DIN rail spring)

RS-485 communication requires an electrical termination of the communication line. The following is necessary:

• 2 resistors of 120 Ohms each at both line ends (to avoid signal reflections)
• a pull-up resistor at RxD/TxD-P and a pull-down resistor at RxD/TxD-N. These 2 resistors care for a defined high level on the bus, while there is no data exchange.

In every RS-485 network 1 pull-up and pull-down resistors must be activated. It is recommended to activate the pull-up and the pull-down resistors at the bus master. These 2 resistors are integrated inside the TK506 RS-485 isolator. They can be activated by connecting the terminals 1-2 and 3-4 of the terminal block with cable bridges.

Electrical Connection: Modbus Protocol

The following figure shows an RS-485 bus with the bus master at the line end.

1	Master at the bus line end, pull-up and pull-down activated, bus termination with 120 Ohms resistors
2	Slave within the bus line
3	Slave at the bus line end, bus termination with 120 Ohms resistors

If the master is located within the bus line, it does not need a terminating resistor. The pull-up and the pull-down resistors, however, are necessary:

1	Slave at the bus line end, bus termination with 120 Ohms resistors
2	Master within the bus line, pull-up and pull-down activated
3	Slave within the bus line
4	Slave at the bus line end, bus termination with 120 Ohms resistors

Attention

:strong:Risk of EMC disturbances!

Unshielded cables may cause EMC disturbances.

Always use shielded cables and connect the shield at every device.

Attention

:strong:Risk of malfunctions!

The pull-up resistors must be used only one time within a bus line.

Use the pull-up resistors only at 1 master.

The cable shields must be grounded CS31 System Bus.

Electrical Connection: CS31 Protocol

The following figure shows an CS31 Bus with the bus master at the line end.

1	Master at the bus line end, pull-up and pull-down activated, bus termination with 120 Ohms resistors
2	Direct grounding clip or steel plate

If the master is located within the bus line, it does not need a terminating resistor. The pull-up and the pull-down resistors, however, are necessary:

1	Master at the bus line end, pull-up and pull-down activated, bus termination with 120 Ohms resistors
2	Direct grounding via clip or steel plate

Attention

:strong:Risk of EMC disturbances!

Unshielded cables may cause EMC disturbances.

Always use shielded cables and connect the shield at every device.

Technical Data

The System Data of AC500 and S500 System Data AC500 are valid here. Only additional details are therefore documented below.

Physical link		RS-485
Electrical Isolation		Yes
Usage / Supported protocols		Modbus (Master and Slave) CS31 (Master only)
Supported baudrates [baud]
	Modbus	9.6 k, 14.4 k, 19.2 k, 38.4 k and 187.5 k
	CS31 system bus	187.5 k
Connector at the communication line		5 pole screw terminal block
Connector at PM554 or PM564		SUB-D, 9-pin, male
Cable type and specification		Twisting rate minimum 10 per meter, with common shield Capacitance between the cores: < 55 nF/km Characteristic impedance: 120 Ω
	Recommended cable cross section	Conductor cross section 0.5 mm² Resistance per core: < 40 Ω/km
	Thinnest cable cross section	Conductor cross section 0.22 mm² Resistance per core: < 100 Ω/km
Max. cable length for Modbus
	at 38.4 kBaud or below	1200 m with cable cross section 0.5 mm² or 400 m with cable cross section 0.22 mm²
	at 187.5 kBaud	500 m with cable cross section 0.5 mm² or 400 m with cable cross section 0.22 mm²
Max. cable length for CS31 system bus		500 m with cable cross section 0.5 mm² or 400 m with cable cross section 0.22 mm²
Specification for external termination resistor		120 Ω, 1 %, 0.25 W
Length		0.6 m
Weight		80 g

Ordering Data

Ordering No.	Scope of delivery
1SAP 186 100 R0001	TK506, RS-485 isolator D-SUB/5-pole terminal