MKS MF1 - Cable; Power

Chapter 5: Process Interfaces
79
4W-Modbus Pinout
Pin IDv Signal EIA/TIA 485
Name
Description
8 RXD0 A’ Receiver terminal 0, Va’ Voltage
(Va’ > Vb’ for binary 0 [ON] state)
Receiver terminal 1, Vb’ Voltage
(Vb’ > Va’ for binary 1 [OFF] state)
3 PMC -- Port Mode Control
Open Æ 2W-Mode
Low level (connected with Common) Æ 4W-
Mode
5 TXD1 B Generator terminal 1, Vb Voltage
(Vb > Va for binary 1 [OFF] state)
9 TXD0 A Generator terminal 0, Va Voltage
(Va > Vb for binary 0 [ON] state)
2 VP -- DC Power Supply
Positive 20 to 30 V
1 Common C/C’ Signal and Power Supply Common
Port mode control: PMC circuit ( TTL compatible ). The port mode is controlled by this external
circuit. In the first case while an open circuit PMC will ask for the 2W-MODBUS mode, a Low level
on PMC will switch the port into 4W-MODBUS Mode.
Power
The MF1 could be powered via the Phönix MC-Series connector below the Zero switch or via the
Sub D connector. Therefore a mating connector is included in the delivery. For the correct power
supply specification see the technical specification in Appendix A. The Pin 1 of the 9 Pin Sub D
connector is connected with the Phönix connector Pin “-“. If the Phönix connector is used for power
supply the Pin 1 of the Sub D connector must not be connected and vice versa.
Cable
A MODBUS over Serial Line Cable must be shielded. At one end of each cable its shield must be
connected to protective ground. If a connector is used at this end, the shell of the connector is
connected to the shield of the cable.
An RS485-MODBUS must use a balanced pair (for D0-D1) and a third wire (for the Common). In
addition to that a second balanced pair must be used in a 4W-MODBUS system (for RXD0-RXD1).
For RS485-MODBUS, Wire Gauge must be chosen sufficiently wide to permit the maximum length
(1000 m). AWG 24 is always sufficient for the MODBUS Data.
Category 5 cables may operate for RS485-MODBUS, to a maximum length of 600 m.
For the balanced pairs used in an RS485-system, a characteristic impedance with a value higher
than 100 Ohms may be preferred, especially for 19200 and higher baud rates.