Appendix b: cabling, Cabling considerations, Rs-232 cabling – Maple Systems OIT Family (ASCII) User Manual

Page 59: Rs-485 cabling

APPENDIX B: Cabling

Cabling Considerations

When an OIT Family Operator Interface Terminal is configured with the ASCII Slave proto-

col, it can communicate to an ASCII host using RS-232 or RS-485 5-wire (full duplex) com-

munications. Hardware handshaking (CTS/RTS) and software handshaking (XON/XOFF)

are not supported.

The RS-232 format is the most common method of connecting to an ASCII host, RS-485 for-

mat is recommended for electrically noisy environments where cable lengths exceed the

RS-232 50 foot specification, and when the application requires more than one OIT.

RS-232 Cabling

RS-232 communications requires three wires: TxD, RxD, and Signal Ground for proper op-

eration. The exact pinout connections required depend upon the ASCII host and OIT model

used. Refer to Figure 4 for the proper OIT RS-232 pinouts. We recommend using cables that

have low-capacitance grade wire with at least 24 gauge. The cable should have an overall

foil shield and chassis ground wire. Twisted pair wires should not be used for RS-232 com-

munications. RS-232 communications has a maximum distance of approximately 50 feet

and is not recommended for electrically noisy or harsh environments.

RS-485 Cabling

RS-485 communications requires five wires: TxD+, TxD-, RxD+, RxD-, and Signal Ground

for proper operation. The exact pinout connections required depend upon the ASCII host

and OIT model used. Refer to Figure 5 for proper OIT RS-485 pinouts. We recommend us-

ing cables that have low-capacitance grade wire with at least 24 gauge. The cable should

have an overall foil shield and chassis ground wire. The cable should have twisted pairs with

the transmit signals (TxD+ and TxD-) on one pair and the receive signals (RxD+ and RxD-)

on another pair. Improper pair matching will result in cross-talk between the transmit and re-

ceive lines and may result in loss of communications. RS-485 communications has a maxi-

mum distance of approximately 5000 feet.

OIT Family Operation Manual (ASCII)

1010-0088, REV02

HOST CONTROLLER

TxD

OIT3160A/OIT3200B

OIT3250B/OIT4160A

OIT4400B/OIT4450B

PORT 1

OIT3600B

RxD

SIG GND

RxD
TxD
SIG GND

2
3
5

Figure 5 RS-232 Pinouts