Denso Power Net Terminal BHT-7500 Spécifications télécharger pdf (Page 169)

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9.4 Event (of Keystroke) Trapping

[ 1 ] Overview

If any of the function keys previously specified for keystroke trapping is pressed, event trapping

makes the program cause an interrupt so as to transfer control from the current program to the

specified event-handling routine.

This trapping facility checks whether any of the function keys is pressed or not between every

execution of the statements.

[ 2 ] Programming for trapping keystrokes

To trap keystrokes, use both the ON KEY...GOSUB and KEY ON statements. The ON

KEY

...GOSUB statement designates the key number of the function key to be trapped and the

event-handling routine (to which control is to be transferred if a specified function key is

pressed) in its label. The

KEY ON statement activates the designated function key.

This trapping cannot take effect until both the

ON KEY...GOSUB and KEY ON statements have

been executed.

The keystroke of an unspecified function key or any of the numerical keys cannot be trapped.

The following program sample will trap keystroke of function keys F1, F2, and F3 (these keys

are numbered 1, 2, and 3, respectively).

ON KEY (1) GOSUB sub1

ON KEY (2) GOSUB sub2

ON KEY (3) GOSUB sub3

KEY (1) ON

KEY (2) ON

KEY (3) ON

(Main routine)

END

sub1

(Event-handling routine 1)

RETURN

sub2

(Event-handling routine 2)

RETURN

sub3

(Event-handling routine 3)

RETURN

1 2 ... 164 165 166 167 168 169 170 171 172 173 174 ... 559 560

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Denso Power Net Terminal BHT-7500 Spécifications Page 169

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