CPU
S
pecifications
and
Operation
4--19
CPU Specifications and Operation
DL105 PLC User Manual, 3rd Edition
The CPU processes the program from address 0 to the END instruction. The CPU
executes the program left to right and top to bottom. As each rung is evaluated the
appropriate image register or memory location is updated. The time required to
solve the application program depends on the type and number of instructions used,
and the amount of execution overhead.
Just add the execution times for all the instructions in your program to determine to
total execution time. Appendix C provides a complete list of the instruction execution
times for the DL105 Micro PLC. For example, the execution time for running the
program shown below is calculated as follows:
Instruction
Time
STR X0
3.3
μ
s
OR C0
2.7
μ
s
ANDN X1
2.7
μ
s
OUT Y0
3.4
μ
s
STRN C100
3.9
μ
s
LD K10
62
μ
s
STRN C101
3.9
μ
s
OUT V2002
60
μ
s
STRN C102
3.9
μ
s
LD K50
62
μ
s
STRN C103
3.9
μ
s
OUT V2006
60
μ
s
STR X5
3.3
μ
s
ANDN X10
2.7
μ
s
OUT Y3
3.4
μ
s
END
27
μ
s
TOTAL
308.1
μ
s
Overhead DL105
Minimum
0.86 mS
Maximum
3.85 ms
X0
X1
Y0
OUT
C0
C100
LD
K10
C101
OUT
V2002
C102
LD
K50
C103
OUT
V2006
X5
X10
Y3
OUT
END
The program above takes only 308.1
μ
s to execute during each scan. The total scan
time is the sum of the program execution plus the overhead as shown above.
“Overhead” includes all other housekeeping and diagnostic tasks. The scan time will
vary slightly from one scan to the next, because of fluctuation in overhead tasks.
NOTE:
You can move words to EEPROM from within the application program. This
can add up to 10ms per 32 word boundary.
Program Control Instructions
— the DL105 PLCs have an interrupt routine
feature that changes the way a program executes. Since this instruction interrupts
normal program flow, it will have an effect on the program execution time. For
example, a timed interrupt routine with a 10 mS period interrupts the main program
execution (before the END statement) every 10 mS, so the CPU can execute the
interrupt routine. Chapter 5 provides detailed information on interrupts.
Application
Program Execution
Summary of Contents for DL105
Page 2: ...DL105 PLC User Manual Manual Number D1 USER M...
Page 308: ...1B DL105 Error Codes In This Appendix Error Code Table...
Page 314: ...1C Instruction Execution Times In This Appendix Introduction Instruction Execution Times...
Page 324: ...1D Special Relays In This Appendix DL105 PLC Special Relays...
Page 327: ...1E PLC Memory In This Appendix DL105 PLC Memory...