21: PID INSTRUCTION21-2 « FC4A MICRO SMART USER ’S MANUAL »PID (PID Control)Applicable CPU Modules and Quantity of PID InstructionsA maximum of 8 or 14 PID instructions can be used in a user program, depending on the CPU module type.Valid OperandsFor the valid operand number range, see pages 6-1 and 6-2.Source operand S1 (control register) uses 27 data registers starting with the operand designated by S1. Data registers D0through D1273 and D2000 through D7973 can be designated by S1. For details, see the following pages.Source operand S2 (control relay) uses 8 points of outputs or internal relays starting with the operand designated by S2.Outputs Q0 through Q300 and internal relays M0 through M1270 can be designated by S2. For details, see page 21-11.Source operand S3 (set point): When the linear conversion is disabled (S1+4 set to 0), the valid range of the set point (S3)is 0 through 4095 which can be designated using a data register or constant. When the linear conversion is enabled (S1+4set to 1), the valid range is –32768 to 32767 that is a value after linear conversion. Use a data register to designate a nega-tive value for a set point when the linear conversion is used. For details, see page 21-12.Source operand S4 (process variable) is designated using a data register allocated as analog input data of the connectedanalog I/O module, such as D760 or D766. See page 24-8. To read input data from an analog I/O module, designate aproper data register number depending on the slot position of the analog I/O module and the analog input channel numberconnected to the analog input source. For details, see page 21-13.Destination operand D1 (manipulated variable) stores –32768 through 32767 that is a calculation result of the PID action.For details, see page 21-13.FC4A-C10R2/C FC4A-C16R2/C FC4A-C24R2/C FC4A-D20K3/S3 FC4A-D20RK1/RS1 & FC4A-D40K3/S3— — X (8) X (8) X (14)Operand Function I Q M R T C D ConstantS1 (Source 1) Control register — — — — — — D0-D7973 —S2 (Source 2) Control relay — Q0-Q300 M0-M1270 — — — — —S3 (Source 3) Set point — — — — — — D0-D7999 0-4095S4 (Source 4) Process variable (before conversion) — — — — — — D0-D7999 —D1 (Destination 1) Manipulated variable — — — — — — D0-D7999 —When input is on, auto tuning and/or PID action is exe-cuted according to the value (0 through 2) stored in adata register operand assigned for operation mode.D1*****S1*****PID S2*****S3*****S4*****
