User's Guide

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minute and the inactive timer is set to five minutes. The slow poll timer’s value is
always less then that of the inactive timer.
The base station polls the fast poll sub stations until one minute has passed. Then it
polls the sub stations on the slow poll list, then moves back to poll the fast poll sub sta-
tions, and continues in this fashion until five minutes has passed. The base station then
polls the inactive sub station and always broadcasts an ADP packet, if ADP is enabled.
Error Detection and Recovery
I-frames (data frames) can contain several Bridged-Ethernet frames or routed IP data-
grams. They are sequence numbered: Ns is the frame number, Nr is an ACK, meaning
all frames 'r' were received.
If the base station gets an I-frame out of sequence, it assumes one was missed and
sends out a reject packet. Errors are handled as follows:
• If Ns gets ahead by one, the packet is rejected. The other side retransmits.
• If Nr changes and a frame is acknowledged but was not sent out, the base
sends back a disconnect to the sub station, or the sub station sends a FRMR
(Frame reject response) to the base station. This is a logical disconnect, the RF
physical link is maintained.
• The sub station resets and the base makes an attempt to re-establishes the RF-
DLC session on the next polling cycle.