Using FDL
63
To set up a message, set:
• bits in the Control/Config register, CntCfg, if necessary
If you set bit 2, the scanner sends the message to the high priority
queue on the scanner. The scanner maintains two FDL message
queues. When it gets the token, the scanner can send one message
from the high priority queue when it gets the token, even if the token
hold time has expired.
If you set bit 4 in the CntCfg register, the scanner does not include
this message block when it is displaying the status of FDL messages
on the LED.
• the destination station, DstStn. The allowed range is 0 to 126.
• the destination SAP, DstSap, if required. This is almost always
needed. The default value is 255, which means the message gets sent
to the default SAP at the destination. You usually send the message
to some specific SAP. The allowed range is 0 to 63, or 255.
When you send a message with a destination SAP, the scanner
automatically sets the high bit in the destination station number
when it sends the message. Do not set the high bit when you set the
destination station number.
• the source SAP, SrcSap, if required. If you are sending a destination
SAP, you almost always want to send a source SAP. The default
value is 255. The use of the source SAP is application and module
dependent; the destination station may or may not require or use the
source SAP.
Note
This high priority refers to how the message is processed by
the scanner in getting it out on the network and has nothing
to do with a high priority frame control value. For example,
if the message type is SRDL, the message is processed as a
low priority message at the destination.
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