Siemens SIMATIC TIWAY 1 User Manual page 57

OPERATION AND APPLICATION
2.10.10.3 Adjusting An HIUs Bandwidth
The REPORT NETWORK BANDWIDTH ALLOCATION command, code 36,
returns counters that reflect the relative network activity for a specific HIU.
The counters do not reset after reaching their maximum value and must be
explicitly reset.
Although the HIUs on the network have no direct control over the number of
Network Manager buffers allocated to them, they can control how those buffers
are used with the ALLOCATE HIU BANDWIDTH command. This command
defines how the buffers are to be divided between direct requests/non-repetitive
macros and repetitive macros by specifying how many of the allocated buffers
will be used for repetitive macros. By default, repetitive macros can use all of the
NM buffers allocated to the HIU. This command also limits the number of
outstanding requests for a single secondary device, preventing one secondary
from dominating the entire bandwidth. The default for this parameter is the
smaller of two requests per secondary or the number of NM buffers allocated to
the HIU. Both parameters are single bytes ranging from 00 to the number of
NM buffers allocated to the HIU. The command code will be returned if the
command is accepted. Your applications software may issue this command more
than once in order to change the parameters to match the demands as they
change.
Issue the REPORT HIU BANDWIDTH ALLOCATION command to determine
the buffer allocation and retrieve macro statistical counters. The statistical
counter parameters are long words that must be explicitly reset when they
reach their maximum values. The command string includes the command code
and the optional reset counters code.
There are two sets of counters, one for repetitive macros and the other for
non-repetitive macros. The first counter in each set counts the number of
I-Frame pairs sent and received by the macro type. The second counter in each
set counts the number of I-Frame bytes sent by the macro type. The third
counter in each set counts the number of I-Frame bytes received by the macro
type. These counts do not include any HDLC overhead or communications
counts between the NM and the HIU. Reset these counters by sending the
command string 1A 01. The adapter will return the command code 1A if
accepted.
2–47 UNILINK HOST ADAPTER
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