Siemens CPU 948 User Manual

10.9 Applications
Based on examples, this section explains how to program
multiprocessor communication.
Note
If you use the function blocks listed below and service interrupts
on your CPU (e.g. with OB 2) remember to save the "scratchpad
flags" at the start of interrupt servicing and to write them back
when the interrupt is completed.
This also applies to the setting "interrupts at block boundaries",
since the call of the special function organization blocks
represents a block boundary.
10.9.1
Calling the Special
Function OB using
Function Blocks
The following five function blocks (FB 200 and FB 202 to FB 205)
contain the call for the corresponding special function organization block
for multiprocessor communication (OB 200 and OB 202 to OB 205).
The numbers of the function blocks are not fixed and can be changed.
The parameters of the special function OBs are transferred as actual
parameters when the function blocks are called. The direct call of the
special function organization blocks is faster, however, is more difficult
to read owing to the absence of formal parameters
FB no. FB name Function
FB 200
FB 202
FB 203
FB 204
FB 205
INITIAL
SEND
SEND-TST
RECEIVE
RECV-TST
Set up buffer
Send a data field
Test sending capacity
Receive a data field
Test receiving capacity
The flag area from FY 246 to maximum FY 255 is used by the function
blocks as a parameter field for the special function organization blocks.
The exact significance of the input and output parameters is explained
in the description of the special function organization blocks.
Applications
CPU 948 Programming Guide
C79000-G8576-C848-04
10 - 53

Siemens CPU 948 Specifications

General

Brand	Siemens
Model	CPU 948
Category	Controller
Language	English