Hardware Handshaking (Ready/Busy). Digi DigiBoard PC/16e, DigiBoard COM/8i, DigiBoard PC/8i, DigiBoard MC/16i, DigiBoard PC/16i, DigiBoard MC/4i, DigiBoard MC/ i Series, DigiBoard COM/4i, DigiBoard PC/ i Series, DigiBoard MC/8i

DB-25 Equipped Boards

Software Handshaking (XON/XOFF)

In most cases, serial terminals and printers need only a “three-wire” connection to the board. All DigiBoard device driver software supports XON/XOFF

(software) handshaking, so the only signal lines necessary are Transmitted Data

(TxD), Received Data (RxD) and Signal Ground (SG). It may be necessary to disable DCD (Data Carrier Detect) sensing through a software command—see your DigiBoard device driver software manual for instructions. Cables must be shielded to remain in compliance with FCC certification requirements, and the shield should be connected to Chassis Ground (GND) at both ends of the cable run.

A simple cable for connecting a terminal or a printer to a DB-25 equipped board is shown in Figure 23.

Figure 23 Simple Terminal/Printer Cable (DB-25)

DB-25 Female

Signal Pin

(

GND

TxD

RxD

RTS

CTS

DSR

SG

DCD

DTR

RI

Shell

2

3

4

5

6

7

8

20

22

Cable Shield)

DB-25 Male

Pin Signal

4

5

6

7

1

2

3

8

20

22

GND

TxD

RxD

RTS

CTS

DSR

SG

DCD

DTR

RI

The cable shown in Figure 23 is a three-wire null modem cable—that is,

Transmitted Data on one end of the cable is connected to Received Data at the other end, and vice versa.

The male DB-25 end can be plugged directly into most serial terminals and printers without any adapters. The female DB-25 end plugs directly into one of the DB-25 connectors on the fan out cable or connector box assembly.

40 DigiBoard Intelligent Serial Communications Boards