IDEC MicroSmart - Manual (Page 368)

21: PID I NSTRUCTION
21-12 « FC4A M ICRO S MART U SER ’ S M ANUAL »
S2+2 Output Manipulated Variable Limit Enable
The output manipulated variable upper limit (S1+16) and the output manipulated variable lower limit (S1+17) are enabled
or disabled using the output manipulated variable limit enable control relay (S2+2).
To enable the output manipulated variable upper/lower limits, turn on S2+2.
To disable the output manipulated variable upper/lower limits, turn off S2+2.
S2+3 Integral Start Coefficient Disable
The integral start coefficient (S1+10) is enabled or disabled using the integral start coefficient disable control relay (S2+3).
To enable the integral start coefficient (S1+10), turn off S2+3; the integral term is enabled as specified by the integral start
coefficient (S1+10).
To disable the integral start coefficient (S1+10), turn on S2+3; the integral term is enabled at the start of the PID action.
S2+4 High Alarm Output
When the process variable (S1+0) is higher than or equal to the high alarm value (S1+14), the high alarm output control
relay (S2+4) goes on. When S1+0 is lower than S1+14, S2+4 is off.
S2+5 Low Alarm Output
When the process variable (S1+0) is lower than or equal to the low alarm value (S1+15), the low alarm output control relay
(S2+5) goes on. When S1+0 is higher than S1+15, S2+5 is off.
S2+6 Control Output
During auto tuning in auto mode with the auto/manual mode control relay (S2+1) set to off, the control output (S2+6) is
turned on and off according to the AT control period (S1+20) and AT output manipulated variable (S1+22).
During PID action in auto mode with the auto/manual mode control relay (S2+1) set to off, the control output (S2+6) is
turned on and off according to the control period (S1+13) and the output manipulated variable (S1+1) calculated by the
PID action.
In manual mode with the auto/manual mode control relay (S2+1) set to on, the control output (S2+6) is turned on and off
according to the control period (S1+13) and the manual mode output manipulated variable (S1+18).
S2+7 AT Complete Output
The AT complete output control relay (S2+7) goes on when auto tuning is complete or failed, and remains on until reset.
Operating status codes are stored to the operating status control register (S1+2). See page 21-4.
Source Operand S3 (Set Point)
The PID action is executed to adjust the process variable (S1+0) to the set point (S3).
When the linear conversion is disabled (S1+4 set to 0), set a required set point value of 0 through 4095 to the operand des-
ignated by S3. Valid operands are data register and constant.
When the linear conversion is enabled (S1+4 set to 1), designate a data register as operand S3 and set a required set point
value of –32768 through 32767 to the data register designated by S3. Since the PID instruction uses the word data type,
negative constants cannot be entered directly to operand S3. Use the MOV instruction with the integer (I) data type to store
a negative value to a data register. The set point value (S3) must be larger than or equal to the linear conversion minimum
value (S1+6) and smaller than or equal to the linear conversion maximum value (S1+5).
When an invalid value is designated as a set point, the PID action is stopped and an error code is stored to the data register
designated by S1+2. See Operating Status on page 21-4.