Edwards SCU-800

SCU-800 Control Unit for Turbomolecular Pump
MT-49E-101-G
Page 60
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.
 After receiving commands, SIM will return a response approximately 5 msec later
*1
. Use the PC
of which transmit/receive switch time is 5 msec or less.
 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.
(SCU-800 does not have terminator setting function)
PC
7 (D–)
8 (D+)
120Ω
120Ω
SIM
(connector X3
or X6)
a) RS485 single point connection
PC
7 (D–)
8 (D+)
120Ω
7 (D–)
8 (D+)
120Ω
7 (D–)
8 (D+)
SIM 1
(connector X3
or X6)
SIM 2
(connector X3
or X6)
SIM N
(connector X3
or X6)
b) RS485 multi-point connection
Figure 34 - RS485 connections
*1
Software version 63_A 1.2 or later.