Rockwell Automation 1771-DB BASIC MODULE - Manual (Page 157)

Chapter
Statements 11
11 -5
Use the CLOCK1 statement to enable the free running clock resident on
the BASIC module. The special function operator TIME (page 9 -19)
increments once every 5 milliseconds after you execute CLOCK1.
CLOCK1 uses an internal timer to generate an interrupt once every
5 milliseconds. Because of this, the special function operator TIME has a
resolution of 5 milliseconds. The special function operator TIME counts
from 0 to 65535.995 seconds. After reaching a count of 65535.995
seconds TIME overflows back to a count of 0. The interrupts associated
with CLOCK1 cause the module programs to run at about 99.6% of normal
speed. This means that the interrupt handling for the free running clock
uses about 0.4% of the total CPU time.
Important: This does not include additional overhead for ONTIME user
interrupt handling execution.
Syntax
CLOCK1
Example
>10 TIME = 0
>15 DBY(71) = 0 :REM RESET NONINTEGER PORTION OF TIME
>20 CLOCK1
>30 ONTIME 2,100
>40 DO
>50 WHILE TIME < 10
>60 END
>100 PRINT “TIMER INTERRUPT AT – ”,TIME,“ SECONDS”
>110 ONTIME TIME+2,100
>120 RETI
READY
>RUN
TIMER INTERRUPT AT – 2.01 SECONDS
TIMER INTERRUPT AT – 4.015 SECONDS
TIMER INTERRUPT AT – 6.01 SECONDS
TIMER INTERRUPT AT – 8.01 SECONDS
TIMER INTERRUPT AT – 10.01 SECONDS
CLOCK1