Siemens SIMATIC TIWAY 1 - Manual (Page 123)

HOST COMMAND SET REFERENCE
UNILINK HOST ADAPTER 5–38
USER MANUAL
5.4.10 Allocate HIU Bandwidth — 19
The ALLOCATE HIU BANDWIDTH command allows an adapter configured as
an HIU to control how the NM buffers allocated for its use will be used. The
Network Manager allocates a fixed number of NM buffers for the HIU’s use,
which is the HIU’s bandwidth. This bandwidth processes direct commands,
non-repetitive macros, and repetitive macros. Since repetitive macros are
always ready for transmission, they will tend to use the entire bandwidth,
slowing down the response for direct commands and non-repetitive macros. The
first parameter for this command specifies a limit on the number of NM buffers
that can be used for repetitive macros.
The second parameter is to limit the number of outstanding requests for a single
secondary device. This prevents a single secondary device from getting the
entire bandwidth, thus leaving no room for requests for other secondaries. It
also prevents one HIU from dominating a secondary device and increasing its
access delay for other HIUs.
This command may issued at any time after the HIU has been initialized and
the bandwidth allocated by the Network Manager. This helps tailor the
bandwidth to changing network conditions.
Command: 19 ll nn
Response: 19
Usage: PERFORMANCE
Modes: MHIU, HIU
Parameters:
ll The maximum number of repetitive macros that can be executing
at one time. Values range from 0 to the number of NM buffers
allocated by the Network Manager and will default to the number
of NM buffers allocated by the Network Manager.
nn The number of outstanding requests per secondary. Values range
from one to the number of NM buffers allocated by the Network
Manager and will default to two requests per secondary or the
number of NM buffers allocated by the Network Manager,
whichever is smaller.