Rockwell-automation 2708-NBD VBASIC Language Development Kit Instrukcja Użytkownika Pobierz pdf (Strona 37)

Chapter 4

Special Devices in A-B VBASIC

4–16

Reserved device name: EGG

Description:

The egg timer is a word of memory which, when non-zero, is decremented

by one every 1/100 second.

These statements, when used with the file number associated with an OPEN

“EGG”, control this timing device:

SEEK statement: sets the timer to an integer or long

For example:

OPEN “EGG” FOR INPUT AS #4

SEEK #4, 1000

sets the timer to reach 0 in ten seconds.

SEEK function: returns the current value of the timer as a LONG value.

(LONG is used to avoid sign confusion for values over 32767 with an

INTEGER).

LOF and LOC also return the timer’s current value.

EOF returns TRUE (-1) when the timer “goes off” by reaching zero. This

device is an easy way to implement delays and timeouts without the midnight

rollover problem associated with TIME$ and TIMER.

Device: The Egg Timer

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Rockwell-automation 2708-NBD VBASIC Language Development Kit Instrukcja Użytkownika Strona 37