Siemens SIMATIC TIWAY 1 - Manual (Page 56)

OPERATION AND APPLICATION
UNILINK HOST ADAPTER 2–46
USER MANUAL
2.10.10.2 NM Buffer Allocation
These buffers are allocated implicitly with the background monitor function.
However, the NM function in an adapter in the MHIU/EHA mode does not
support background monitor or multiple hosts. The value specified for
Option–09 of the CONFIGURE NETWORK MANAGER command will be
allocated to each HIU function as the NM function brings it online. If no value
was specified for Option–09, the value will default to one fourth of the available
buffers.
An amount other that the default number of buffers can be allocated explicitly
with the ALLOCATE NETWORK MANAGER BUFFERS command when the
number of buffers allocated by the background monitor is zero or if issued before
the NM function is enabled by the CONFIGURE NETWORK MANAGER
command. The ALLOCATE NETWORK MANAGER BUFFERS command can
only be issued by the host computer attached to the adapter functioning the
Network Manager and can only be issued once for each as HIU. After the buffers
are allocated, they will remain allocated until the NM or MHIU is reset.
The adapter will return the command code and the HIU address if the
ALLOCATE NETWORK MANAGER BUFFERS command is accepted. Your
applications software can issue the REPORT NETWORK MANAGER
BUFFERS AVAILABLE command to determine how many buffers are unused.
To use it, send the one byte command, code 35. The adapter will return the
command code, the total number of NM buffers, and the number of NM buffers
available.