User`s guide

buffer has the same command and queue value sent in step 2, and also
contains the data and checksum. Upon completion of this transfer, the
SLTA-10 Adapter returns to the NORMAL state.
The network driver must preserve the continuity of the type of buffer
request and the type of message sent downlink.
For example, if the
network driver sends the niCOMM+niTQ-P command requesting a priority
output buffer, and follows this with a message transfer with the non-
priority niCOMM+niTQ command, the SLTA-10 Adapter will incorrectly
store the message in a priority output buffer, the type originally requested.
Up/ink Flow Cot-&o/ Profocol
Uplink traffic may be incoming LonTalk messages, output buffer request
acknowledgments, completion events, or local commands. The network
driver translates the interface buffers to application buffer format and
stores the buffers in a queue until the host application is ready to read
them.
There is no buffer request protocol for uplink traffic.
The network driver is
normally assumed to have sufficient buffers. The network driver can
suspend or resume uplink traffic when no network driver input buffers are
available by sending the Uplink Source Quench (niPUPXOFF) command to
the SLTA-10 Adapter. This prevents the STLA from sending any LonTalk
messages uplink. When the network driver senses that network driver
input buffers are available, it sends the Uplink Source Resume (ni PUPXON)
command to resume uplink transfers. Figure 9.6 summarizes the uplink
state transitions.
Node
1 Reset
Receive
niPUPXOFF?
Receive
niPUPXON?
Note:
Responses to niNETMGMT and niSSTATUS commands are allowed in the Flush state.
Figure 9.6 SLTA-10 Adapter Uplink Flow Control States
The host may chose to sidestep the downlink buffer request protocol. In
this case, the complete message is sent downlink without any buffer request
step. If the SLTA-10 Adapter has a free output buffer, then the message
will be transferred into the SLTA-10 Adapter successfully. If not, there will
be no indication and the message will be lost. The exception to this case is
when using the transport layer protocol, in which case the SLTA-10
Adapter will send the NACK to the host, which should force the host to re-
send the message. Otherwise, in order to use this feature successfully, the
host driver must manage the number of available output buffers within the
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SLTA-10 Adapter User’s Guide
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