Rockwell-automation 1771-DB BASIC MODULE Instrukcja Użytkownika Pobierz pdf (Strona 43)

Chapter

Using the Communication Ports

2 -5

Hardware Handshaking

The BASIC module uses these rules when hardware handshaking is

enabled. The BASIC module:

does not transmit until CTS, DCD, and DSR become active

examines DSR and DCD following the receipt of a character. If the

DSR and DCD are active, the character is placed in the input queue.

If DSR or DCD is inactive, the character is assumed to be noise and is

discarded.

Important: You need to know whether the device connecting to the

BASIC module has a DTE or DCE interface.

The BASIC module serial ports are configured as 25-pin Data Terminal

Equipment (DTE), as are most terminals or computer ports.

DTE 25 pinout Signal description Signal from DTE perspective DTE 9 pinout Signal description

TXD–Transmitted Data Output 3

3 RXD–Received Data Input 2

4 RTS–Request to Send Output 7

5 CTS–Clear to Send Input 8

6 DSR–Data Set Ready Input 6

7 Com–Signal Common Shared 5

8 DCD–Data Carrier Detect Input 1 CD–Carrier Detect

20 DTR–Data Terminal Ready Output 4

22 NC–No Connection

(for BASIC module only)

Input 9 RI–Ring Indicator (BASIC

module does not support)

Devices such as modems are Data Communication Equipment (DCE).

Pinouts on these terminals are defined for ease of interfacing with DTE

equipment.

DCE 25 pinout Signal description Signal from DC perspective DCE 9 pinout

TXD–Transmitted Data Input 3

3 RXD–Received Data Output 2

4 RTS–Request to Send Input 7

5 CTS–Clear to Send Output 8

6 DSR–Data Set Ready Output 6

7 Com–Signal Common Shared 5

8 CD–Carrier Detect Output 1

20 DTR–Data Terminal Ready Input 4

22 RI–Ring Indicator Output 9

Important: All signal directions that are listed in the previous two tables

are valid. For example, TXD, Transmitted Data, is a DTE output but is

also a DCE input. The signal description is the same for both the DTE and

DCE but the direction of the signal (perspective) has changed based on

whether you have a DTE

or DCE device.

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