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13. Poll Process

Each association supports a poll process that runs at regular intervals to construct and send packets. It runs continuously to manage the clock filter and reach register.

13.1. Poll Process Variables​

Key variables: hpoll (host poll exponent), last (last poll time), next (next poll time), reach (reach register), unreach (unreach counter).

Parameters: UNREACH=24, BCOUNT=8, BURST flag, IBURST flag.

13.2. Operations​

Main flow: Called every second via clock-adjust process. Checks if next poll time reached. Symmetric (modes 1-2), client (mode 3), and broadcast server (mode 5) send packets. Broadcast client (mode 6) updates variables only.

Burst mode: IBURST for initial sync, BURST for reconnection. Sends BCOUNT (8) packets rapidly.

Reach register: 8-bit shift register tracking last 8 polls. Left-shifts each poll, sets LSB to 1 if valid response received.

Poll interval adjustment: Dynamic adjustment based on network conditions and clock stability. Range from minpoll to maxpoll.

Unreachable handling: Increments unreach counter. May trigger burst mode after reaching UNREACH limit (24).

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