STP-iXR1606 Turbomolecular Pump
MT-79E-001-D
Page 72
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 at the shortest.
Connect 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. (STP-iXR1606 does not have terminator
setting function)
PC
7 (D–)
8 (D+)
120
Ω
120
Ω
SIM
(connector X3
or X4)
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 X4)
SIM 2
(connector X3
or X4)
SIM N
(connector X3
or X4)
b) RS485 multi-point connection
Figure 36 - RS485 connections
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