MKS GE50A - Table 13: Digital Interface - RS485 Using 9 Pin D - Model Code 5; Table 14: RS485 Module Status LED Indicators

Chapter Four: Analog and Digital Interfaces Digital Interface Input and Output Options
40
 Device is powered at operating temperature, preferably for 30 or more minutes.
 Devices subject to ambient temperatures other than room temperature (23º C) should be zeroed under
those conditions.
 Pressure drop and flow across the device is reduced to zero. Depending on the gas panel configuration,
this may be done by one of the referenced procedures. See Chapter 7 Maintenance for zeroing procedures.
RS485 Digital Interface Using 9 Pin D Male Connector
The RS485 MFC has one 9 pin D male connector that provides the communications interface with the RS485
master slave network, electrical power from the network bus, and shielding for the instrument signals. There
are no analog I/O signals on this device.
Table 13: Digital Interface – RS485 Using 9 Pin D – Model Code 5
Pin Number Assignment
Pin 1
Power & Signal Common
Pin 2 + 11 to 25 VDC Power In
Pin 3 No connection
Pin 4 No connection
Pin 5 B/B’ (RS485+)
Pin 6 No connection
Pin 7 RS485 Common
Pin 8 Shield
Pin 9 A/A’ (RS485-)
RS485 Communications Protocol
The MFC controller acts as a slave device on an RS485 multi-drop bus. It continually listens for transaction
requests from the host controller, processes requests addressed to it, and sends replies as needed. For a
complete description of this multi-drop protocol see the MKS Document MKS G-Series MFC, RS485
Supplement, 1046411-001. Please contact MKS for this document.
RS485 Controls and Indicators
The top panel of the MFC contains a zero button and two LED indicators, Error and Comm.
Table 14: RS485 Module Status LED Indicators
LED Status Meaning
Flashing Red The device is online and functioning properly.
The Module Status LED flashes red when receiving commands from Host.
Solid Red
Critical link failure.
The device has detected an error that prevents network communication (Duplicate
MAC_ID or bus-off.)
Dark
Not powered / Not online.
The device is offline or the device is not powered; check the network status LED.