User`s guide

Down/ink Buffer Request Protocol
The network driver receives application buffers from the host application, translates
them to interface buffers, and passes the interface buffers to the SLTA-10 Adapter.
There are two types of downlink commands from the host to the SLTA-10 Adapter-
commands that can be executed directly by the SLTA-10 Adapter, and commands
that need to be buffered in the SLTA-10 Adapter.
Downlink commands that are executed directly by the SLTA-10 Adapter are:
niRESET,
niFLUSH_CANCEL, niONLINE, niOFFLINE, niFLUSH,
niFLUSH_IGN, niPUPXOFF, niPUPXON, niSLEEP, andniSSTATUS.
See the Host Application Programmer’s Guide, Appendix D, for a description of these
commands.
The niSStatus command, when sent downlink, will cause the SLTA-10 Adapter to
respond with a niSStatus command plus one byte of data. In MIP mode, this byte of
data contains the settings of configuration switches, with BAUD0 being the least
significant bit. In NSI mode, this byte of data contains 011 in the least significant
bits followed by the XID information, making the SLTA-10 Adapter NSI mode
consistent with the PCNSI Adapter.
Downlink commands that are buffered in the SLTA-10 Adapter are niNETMGMT (for
network management commands to be executed by the SLTA-10 Adapter itself) and
niCOMM (for messages to be sent out on the network, including network variables,
explicit messages, and network management messages addressed to other nodes).
For these two commands, a buffer request protocol is used to ensure that the
SLTA-10 Adapter has a free application buffer for the data.
The network driver must
first request an output buffer before sending the interface buffer. The network driver
must hold the buffers in an output queue until the SLTA-10 Adapter is ready to
receive them. The network driver takes the SLTA-10 Adapter through 3 states to
request a buffer and send the interface buffer. Figure 9.5 summarizes the downlink
state transitions.
SLTA-10 Adapter User’s Guide
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