Specifications

SECTION 6 COMMUNICATIONS

SECTION 6 - COMMUNICATIONS

TALKING TO THE INDEXER

Anaheim Automation’s SMC40 Programmable Indexers communicate by using the RS232C or RS422

standards. Most computers contain at least one RS232 serial port. Some industrial computers have a

RS422 serial port. To communicate with the SMC40, use connector P1. P1 is used for either R3232 or

RS422, and is set by sliding the two switches to the appropriate direction. P1 is a DB9 Female. To

communicate with subsequent axes, use P2, the RS422 output port. P2 is a DB9 Male, and is always set

for RS422, regardless of the switch setting for P1. The switches affect only the Input Port P1. The

difference between the two types of communications is discussed below.

RS232

This serial communication mode is single ended. This means that for each signal there is one wire, and a

common ground reference used by all the signals. For the four signals, RD, TD, CTS and RTS to be

transmitted, RS232C requires five wires. The signal line maintains levels of +5VDC to +15VDC (LOW

LOGIC INPUT) and -5VDC to -15VDC (HIGH LOGIC INPUT). The receiver for the RS232 looks for a

voltage potential of +3 to +25 volts for a logic LOW, and -3 to -25 volts for a logic HIGH. For a valid logic

level, the voltage must be +/-3 volts. RS232 works well at 9,600 baud over distances of up to 50 feet

maximum. RS232 is susceptible to electrical noise, and should not be used in noisy areas. Always use

the shortest cable connection possible.

Note: Keep control wiring separated from motor cable/wiring.

RS422

To talk to the SMC40 in RS422 set the switch to RS422, and use P2. The RS422 serial communication

standard is differential. This means that from each signal, there are two wires. For the four signals

transmitted there needs to be nine wires including the ground reference. The signal line maintains a

voltage level of up to +12 volts on either line. The polarity of the line switches is used to obtain the logic

levels. For example, if RD+ is more positive than RD- then it is a logic HIGH. If RD- is more positive than

RD+, then it is a logic LOW. For a valid logic level, the voltage difference between RD+ and RD- needs to

be greater than 200 millivolts. RS422 is unsusceptible to noise due to the differential lines. RS422 is

specified at a maximum of 9600 Baud at up to 4000 feet.

RS232C

25 PIN CONNECTOR

FUNCTION RS232 FUNCTION

1 CG Chassis Ground

2 TD Transmit Data

3 RD Receive Data

4 RTS RTS - Request To Send

5 CTS CTS - Clear To Send

7 O VDC SG - Signal Ground

TABLE 12: RS422 Connector Pinout