Standard Input/Output; Tag And Standard Input/Output; Tag Types - Toshiba V Series User Manual

3.4

Standard Input/Output

3.4.1

Tag and standard input/output

The relation between tags, standard input/output and programs is described below.
The standard I/O function consists of PV processing, LP processing and PB processing.
Assuming a general process control circuit here, first of all, a signal from an external sensor is
taken to the input for PV processing. This signal is used as a feedback signal. Then the input
value is converted to an engineering unit value by PV processing and the converted value will
be sent to the input (PV) for PID processing (PID instruction) made by program. The PID
processing calculates necessary manipulated variable in accordance with the set point value
(SV) and the predetermined control parameters and sends its output value (MV) to LP
processing. The LP processing executes necessary output processing for output value (MV)
and sends the manipulated variable to an external final controlling element.
Controller
Program
PID processing
Program
Digital processing
Figure 3-5 Relation between Tags, Standard Input/Output and Programs
3.4.2

Tag types

The tag types handled in the standard input/output are shown below.
Tag instrument variable
Indicator variables (PV)
Controller variables (LP)
Pushbutton variables
(PB)
Note 1: Though data can be exchanged with an upstream device or with other controllers via MC bus,
the number of points that can be exchanged on MC bus is limited. For details, see I.5.1
"Number of tables (tags)"
Note 2: To combine controller variables and indicator variables, it is necessary for the user to set
necessary setting to the controller variables.
6F8C1135
Tag instrument variables
PV
PV processing
SV
Input value
MV
LP processing
Output value
PB processing
FI
Input value
Output value
FO
Standard Input/Output
Table 3-6 Tags
No. of I/O points (Note 1)
128
8
32
3.4 Standard Input/Output
I/O
AI/PI
I/O
AO/PO
I/O
DI
I/O
DO
I/O
Description
• Variables for analog input (instantaneous
value, integrated value) or pulse input
(instantaneous value, integrated value)
• Variables for analog output or pulse output
• Controller variables must be used always
combined with indicator variables. (Note 2)
• Tags for digital input/output
3
43