41
Restrictions on Function Blocks
Section 2-3
No Function Block
Connections
A function block’s input cannot be connected to another function block’s out-
put. In this case, a variable must be registered to transfer the execution status
from the first function block’s output to the second function blocks input.
Downloading in Task Units
Tasks including function blocks cannot be downloaded in task units, but
uploading is possible.
Programming
Console Displays
When a user program created with the CX-Programmer is downloaded to the
CPU Unit and read by a Programming Console, the instances will all be dis-
played as question marks. (The instance names will not be displayed.)
Online Editing
Restrictions
The following online editing operations cannot be performed on the user pro-
gram in the CPU Unit.
• Changing or deleting function block definitions (variable table or algo-
rithm)
• Inserting instances or changing instance names
Note
The instance’s I/O parameters can be changed, instances can be
deleted, and instructions outside of an instance can be changed.
Error-related
Restrictions
If a fatal error occurs in the CPU Unit while a function block definition is being
executed, ladder program execution will stop at the point where the error
occurred.
In this case, the MOV AAA BBB instruction will not be executed and output
variable D200 will retain the same value that it had before the function block
was executed.
Prohibiting Access to
FB Instance Areas
To use a function block, the system requires memory areas to store the
instance’s internal variables and I/O variables.
If there is an instruction in the user program that accesses an address in an
FB instance area, the CX-Programmer will output an error in the following
cases.
FB1
EN
XOUT
FB2
XIN1
XIN2
D100
0.0
FB1
EN
XOUT
FB2
EN
XIN1
XIN2
D100
0.0
D3000
D3000
0.0
Temporary variables
transfer the value from
FB1 to FB2.
FB
EN ENO
AAA BBB
D200
D100
0.0
LD P_On
++ AAA
MOV AAA BBB
10.0
Program
FB definition
Body
Instance name
Fatal error occurs here.
Function block instance
area
Initial value of
start address
Initial value
of size
Allowed data areas
Non-retained
H512
896
CIO, WR, HR, DM, EM
Retained
H1408
128
HR, DM, EM
Timer
T3072
1,024
TIM
Counter
C3072
1,024
CNT
Содержание CS1-H Series
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