Siemens CPU 948, Programming Manual

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The data block in the receiving CPU can be longer or shorter than the
data block to be sent. It is, however, important that the data words
transferred by the SEND function exist in the receiving block;
otherwise the RECEIVE function signals an error.
Example:
10.2.2
How the Transmitter and
Receiver are Identified
Each field of data exchanged between the CPUs is marked with a
number to indicate the source and destination CPU.
The CPUs are numbered so that the leftmost CPU has the number 1
and each subsequent CPU to the right has a number increased by 1.
Example
S5-135U/155U:
Data to be
sent in the
transmitting
CPU: Data
received
in the
receiving
CPU:
Data block: DB 17 DB 17
Data word address: DW 32 to DW 63 DW 32 to DW 63
C
O
R
C
C
P
U
1
C
P
U
2
C
P
U
3
C
P C
P I
M
. .
. .
I Q I I Q
Fig. 10-4 Sender/receiver identification
Multiprocessor Communication
CPU 948 Programming Guide
10 - 16
C79000-G8576-C848-04