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 or iDT-002 (optional accessory). Do not use an internal
terminator and an external terminator at the same time. Communication failure may occur.