Edwards SCU-1600

SCU-1600 Control Unit for Turbomolecular Pump
March 10 68 Issue 1-a
5
SERIAL COMMUNICATION PROTOCOL
5.2.2 Connecting the RS485
Make sure the followings when using the serial port COM1 with RS485 or COM2.
A connection condition is 1 on 1 (single point connection) or 1 on N (multi-point connection).
A maximum number of 32 SIMs are connectable in the multi-point connection.
Use twisted-pair wire in communication cable. The extended communication cables should be 1.2 km
or less.
Connect the terminator to the communication devises at both ends of the transmission line. The
terminator (120 Ω, 0.25 W) is required for connection.
(the SCU-1600 dose not have terminator setting function)
PC
7 (D–)
8 (D+)
120
Ω
120
Ω
SIM
(connector X3
or X7)
a) RS485 single point connection
PC
7 (D–)
8 (D+)
120
Ω
7 (D–)
8 (D+)
120
Ω
7 (D–)
8 (D+)
SIM 1
(connector X3
or X7)
SIM 2
(connector X3
or X7)
SIM N
(connector X3
or X7)
b) RS485 multi-point connection
Figure 36 - RS485 connections
Note: It is recommended to use a communication cable (twisted-pair wire) with shield type, and
connect both terminals to the ground.