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Commands - 75

LOCK

UNLOCK

Tasking Statements

SYNTAX: LOCK

UNLOCK [RETURN]

UNLOCK E XIT

PURPOSE: To lock out interrupts from time critical portions of a program.

REMARK S: When an interrupt occurs from a ON TICK, ON COM$, etc., the current program is interrupted and

the interrupt subroutine is called.

In some cases, especially where time is critical, it is desirable that the current program not be

interrupted until it is completed. W hen the command LO CK is executed, any interr upts will be

latched, but not executed until the UNLOCK command is executed.

The UNLOC K RETU RN is only used at the end of a GOSUB routine. In this case a previous

LOCK must occur in the subroutine. For these commands to prevent any part of a subroutine from

being interrupted, LO CK must be the first line of the subroutine. Therefore, the GOSUB must use a

line number, not a label.

UNLOCK EXIT may be used to quickly get out of a FOR-NEXT, GOSUB, or other nested routine.

EXAMPLE: 10 GOSUB 500

20 IF PRESSURE > 234 THEN ALARM = 1.

500 LOCK

510 PRESSURE = AIN(6) - AIN(0)

520 UNLOCK RETURN

If this construct were not used, an interrupt could occur between lines 500 and 510 and/or between

lines 510 and 520 and delay the alarm flag being set in line 20.

ERROR: none

1 2 ... 103 104 105 106 107 108 109 110 111 112 113 ... 207 208

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Remote-processing CAMBASIC Manuale Utente Pagina 108