Measurement-computing Serial488/4 Manual do Utilizador descarregar pdf (Página 27)

Section 2 Getting Started

2.15

PRINT#1,"OUTPUT0800;P4A1B10C1D1X"

Select port 4 and specify

2 stop bits 19200 baud, no

parity, and 8 data bits

2.5.3 Handshake Configuration

The Serial488/4 uses handshaking to prevent loss of data while both

transmitting and receiving serial data. T he function of handshaking is to

prevent a sender from transmitting more data than a receiver can accept.

The Serial488/4 accomplishes this in one of tw o ways, by using hardware

or software handshaking.

Hardware handshaking utilizes the Request to Send (

RTS

) line of the

serial interface to inform the connected device that the Serial488/4 is able

to accept data. Inversely the Clear to Send (

CTS

) line of the serial interface

is monitored by the Serial488/4 to determine w hether or not the connected

device is able to accept data. The Serial488/4 may be configured to use the

hardware (

RTS/CTS

) handshaking method w ith the

command. In

addition the automatic handshaking control option (

) is normally used.

This option will negate and assert the

RTS

line depending on the amount of

memory available for receiving serial data. The manual handshake control

options,

and

, may be used in special circumstances to un-assert

and assert the

RTS

line under program control if desired. The clock output

handshake control option (

) is not allowed when hardware handshaking

is being used and will generate a command conflict error if attempted.

The software handshaking method uses special control characters,

transmitted along with the serial data, to prevent loss of serial data. The

XOFF

character (

&H11

) is transmitted to inform the connected device that

the Serial488/4 is no longer able to accept data. The

XON

character

(

&H13

) is transmitted to inform the connected device that the Serial488/4

is again able to accept data. Similarly the Serial488/4 monitors the serial

data it receives for the occurrence of

XON/XOFF

control characters and

stops or starts the transmission of data to the connected device accordingly.

The Serial488/4 may be configured for software (

XON/XOFF

) handshaking

by using the

command. In addition the automatic handshaking control

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