Digital I/O Connections

Chapter 2 - Connections

This chapter will cover the connections required for the 485SDD16. There are three sets of connections: digital I/O, serial port, and power supply. Do not make any connections to the 485SDD16 until you have read this chapter.

Connections to the I/O lines are made through the DB25S (female) I/O port connector. Refer to Table 2.1. See Chapter 5 for I/O interfacing examples.

Digital Inputs

The digital input lines are CMOS/TTL compatible and can handle voltages from 0Vdc to +5Vdc.

Digital Outputs

The digital output lines have a maximum voltage of +5Vdc and are CMOS compatible.

Ground

This pin should be connected to the external digital devices ground.

Table 2.1 - 485SDD16 I/O Port Pinout

DB-25S		DB-25S
Pin #	Function	Pin #	Function

1	No connection	14	I/O #15
2	No connection	15	I/O #14
3	No connection	16	I/O #13
4	No connection	17	I/O #12
5	No connection	18	I/O #11
6	No connection	19	I/O #10
7	Ground	20	No connection
8	+12Vdc Input	21	I/O #9
9	I/O #0	22	I/O #8
10	I/O #1	23	I/O #7
11	I/O #2	24	I/O #6
12	I/O #3	25	I/O #5
13	I/O #4

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Serial Port Connections

In order to communicate to the 485SDD16 module it must be connected to an RS-422/RS-485 serial port. The 485SDD16 will work on a 2-wire or 4-wire RS-485 multi-node network. Refer to B&B Electronics’ free RS-422/485 Application Note for more information. The unit automatically detects baud rates from 1200 to 9600. A data format of 8 data bits, 1 stop bit and no parity is used. Connections are made using terminal blocks. Table 2.2 shows the terminal blocks and their functions.

Table 2.2 - RS-485 Terminal Block Connections

		Signal
TB		Direction at	Notes
Label	Signal	485SDD16	Notes

FR	Frame	-	Connection for frame ground.
GND	Ground
TD(A)	Transmit	Output	Connection is required. [Loop to
	Data (A)		RD(A) for 2-wire hookup]
TD(B)	Transmit	Output	Connection is required. [Loop to
	Data (B)		RD(B) for 2-wire hookup]
RD(A)	Receive	Input	Connection is required. [Loop to
	Data (A)		TD(A) for 2-wire hookup]
RD(B)	Receive	Input	Connection is required. [Loop to
	Data (B)		TD(B) for 2-wire hookup]
+12V	+12 Vdc	Input	Connection is required.
	Power
GND	Ground	-	Connection for Signal GND and
			Power Supply GND.

Atypical 2-wire RS-485 connection is shown in Figure 2.3 and a typical RS-422 (or RS-485 4-wire) connection is shown in Figure

2.4.Note that the 485SDD16 data line labels use “A” and “B” designators (per EIA RS-485 Specification). However, some RS-485 equipment uses “+” and “-“ as designators. In almost all cases, the “A” line is the equivalent of the “-“ line and the “B” is the equivalent of the “+” line. With an RS-485/422 system there are other factors that require consideration, such as termination and turn-around delay. For more information refer to B&B Electronics’ free RS-422/485 Application Note.

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PH (815) 433-5100 -- FAX (815) 433-5104

Chapter 2 - Connections