Edwards STP-iS2207 Series - Connecting the RS485

STP-iS2207 Series Turbomolecular Pump
MT-89E-001-C
Page 70
5
SERIAL COMMUNICATION PROTOCOL
5.2.2 Connecting the RS485
Make sure the followings when using the serial port COM1 with RS485.
• 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
external terminator (120 Ω, 0.25 W) is required for connection.
• The internal terminator of the STP side is available. When using it, set it by STP-Link (optional
accessory) or display unit iDT-001 (optional accessory). Do not use an internal terminator and an
external terminator at the same time. Communication failure may occur.
PC
7(D–)
8(D+)
120Ω
120Ω
External
Internal
SIM
(connector X3)
a) RS485 single point connection
PC
7 (D–)
8 (D+)
120Ω
7 (D–)
8 (D+)
120Ω
7 (D–)
8 (D+)
External Internal
SIM 1
(connector X3)
SIM 2
(connector X3)
SIM N
(connector X3)
b) RS485 multi-point connection
Figure 36 - RS485 connections