Page 396 - Programmable Logic Controllers, Fifth Edition - Mobile version

Inputs Ladder logic program
Conveyor_1_Sensor
L1 <Local:1:I.Data.4>
CTU
Count Up CU
Counter Conveyor_1_Parts
Conveyor_1_Sensor
Preset 250 DN
Accum 30
Conveyor_2_Sensor
<Local:1:I.Data.5>
CTU
Count Up CU
Counter Conveyor_2_Parts
Preset 250 DN
Accum 70
Conveyor_2_Sensor
ADD
Add
Source A Conveyor_1_Parts.ACC
30
Source B Conveyor_2_Parts.ACC
70
Dest Conveyor_3_Parts
100
Manual_Conveyor_Reset
Conveyor_1_Parts.DN Conveyor_1_Parts Conveyor_2_Parts
RES RES
Conveyor_2_Parts.DN
Conveyor 1
Manual_Conveyor_Reset
Conveyor 3 <Local:1:I.Data.2>

Conveyor 2
Tag Name Value Style Data Type
Conveyor_1_Parts { . . . } COUNTER
Conveyor_1_Parts.PRE 250 Decimal DINT
Conveyor_1_Parts.ACC 30 Decimal DINT
Conveyor_1_Parts.CU 0 Decimal BOOL
Conveyor_1_Parts.DN 0 Decimal BOOL
Conveyor_2_Parts { . . . } COUNTER
Conveyor_2_Parts.PRE 250 Decimal DINT
Conveyor_2_Parts.ACC 70 Decimal DINT
Conveyor_2_Parts.CU 0 Decimal BOOL
Conveyor_2_Parts.DN 0 Decimal BOOL
Conveyor_1_Sensor 0 Decimal BOOL
Conveyor_2_Sensor 0 Decimal BOOL
Conveyor_3_Parts 100 Decimal DINT
Manual_Conveyor_Reset 0 Decimal BOOL

Figure 15-82 Program used as part of a parts tracking system.

it is logically false. In this example Value_1 (1420) is
greater than Value_2 (1200) so the Greater_Than_PL is
CMP LIM MEQ EQU NEQ LES GRT energized.
The compare (CMP) instruction performs a comparison
Bit Timer/Counter Input/Output Compare
on the arithmetic operations specified by the expression.
Figure 15-83 Compare toolbar for the ControlLogix The expression may contain arithmetic operators, compari-
controller. son operators, and tags. The execution of a CMP instruction

Math, Comparison, and Move Instructions Part 5 377

pet73842_ch15_333-394.indd 377 03/11/15 7:34 PM