User`s manual

10-2 Motion Mate™ DSM314 for Series 90™-30 PLCs User's Manual – January 2001 GFK-1742A
10
Time
2
ms
SLB SLB SLB SLB SLB SLB SLB SLB SLB SLB
2
ms
2
ms
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ms
2
ms
2
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Supervisory
Logic Block
CMOVE PMOVE DWELL PMOVE ETC..
Motion
Program
Motion Program Local Logic Program (Supervisory Logic Block)
CMOVE ##,ABS,SCURVE Position_Loop_TC_1:=50;
PMOVE ##,ABS,SCURVE IF Actual_Position_1>4000 THEN
DWELL ## Digital_Output1_1:=ON;
PMOVE ##,ABS,LINEAR END_IF;
. IF Actual_Position_1>=4500 THEN
. Digital_Output1_1:=OFF;
. END_IF;
. IF Actual_Position_1> 6000 THEN
Digital_Output2_1:=ON;
END_IF;
IF Actual_Position_1>=7500 THEN
Digital_Output2_1:=OFF;
END_IF;
Figure 10-1. Local Logic Versus Motion Program Execution
It is important to understand the concept shown in Figure 10-1 before writing local logic programs.
The local logic program runs to completion each position loop sample period. The program then
re-executes the complete local logic program the next position loop sample period. This execution
method differs from the motion program execution method. The motion programs execute each
command to completion in a sequential fashion, without any time guarantees. To reiterate this
concept, we look at the first four local logic execution periods (reference Table 10-1) for the local
logic and motion programs shown in Figure 10-1. In the example, we note that the local logic
program executes to completion each position loop sample period. The motion program statements
execute until the controlled motion achieves the desired result. For additional details concerning
motion program statement execution consult chapter 7.