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6.1.2
Function Block Diagram
The SVC_REQ function requests the CPU to perform the special service
identified by the FNC operand.
Parameters for SVC_REQ are located in the parameter block, which begins at
the reference identified by the PRM operand. The number of 16-bit references
required depends on the type of special controller service being requested.
The parameter block is used to store both the function's inputs and outputs.
Operands
Note: Indirect referencing is available for all register references (%R, %P, %L, %W, %AI, and %AQ).
Parameter Description
Solve
Calculated by the FBD editor.
Order
EN
Enable input. When set to ON, the
SVC_REQ executes
FNC
Function number; Service Request
number. The constant or variable that
identifies the requested service.
PRM
The first word in the parameter block
for the requested service. Successive
16-bit locations store additional
parameters.
ENO
Set to ON unless an incorrect
function number, incorrect
parameters, or out-of-range
references are specified. Specific
SVC_REQ functions may have
additional causes for failure.
GFK-2950C
Chapter 6. Service Request Function
Allowed Types Allowed Operands
NA
BOOL
Bit reference in a
non-BOOL
variable
INT, DINT, UINT,
WORD, DWORD
INT, DINT, UINT,
WORD, DWORD
BOOL
Bit reference in a
non-BOOL
variable.
February 2018
NA
data flow, I, Q, M, T, G, S, SA, SB, SC,
discrete symbolic, I/O variable
I, Q, M, T, G, R, P, L, AI, AQ, W,
non-discrete symbolic, I/O variable
All except %S - %SC
You can use data flow only if the
parameter block requires only one
WORD
If you use a symbolic variable or an
I/O variable, ensure that its Array
Dimension 1 property is set to a
value large enough to contain the
entire parameter block.
All except flow, %S - %SC and
constant
data flow, I, Q, M, T, G, non-discrete
symbolic, I/O variable
I, Q, M, T, G, R, P, L, AI, AQ, W,
non-discrete symbolic, I/O variable
Optional
No
No
No
No
Yes
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