Technical data

Summary Buffering data on the coordinator COR 923C allows the asynchronous
operation of transmitting and receiving CPUs and compensates for
their different processing speeds.
Since the capacity of the buffer is limited, the receiver should check
"often" and "regularly" whether there are data in the buffer
(RECEIVE TEST function, receiving capacity > 0) and should
attempt to fetch stored data (RECEIVE function). Ideally, the
RECEIVE function should be repeated until the receiving capacity is
zero. This means that the transmitted data are not buffered for a longer
period of time and that the receiver always has the current data. This
also means that memory fields remain free (the transmitting capacity
is increased) and prevents the sender from being blocked (i.e. when
the transmitting capacity is zero).
Note
A receiving capacity of zero represents the ideal state (i.e. all
transmitted data have been fetched by the receiver), on the other
hand a transmitting capacity of zero indicates
incorrect
planning
, as follows:
- the SEND function is called too often,
- the RECEIVE function is not called often enough
or
- there are not enough memory fields assigned to the link.
The capacity of the buffer is insufficient to compensate tempo-
rary imbalances in the frequency with which the CPUs trans-
mit and receive data.
Multiprocessor Communication
CPU 928B Programming Guide
10 - 18 C79000-B8576-C898-01