Bulletins from the Pacific Packet Radio Society - page 138

FLAG DC SC RC CNTL PID TEXT FCS1 FCS2 FLAG

DC - Destination Call, target station for this packet
SC - Source Call, originating station for this packet
RC - Repeater Call, specifies repeater to be used (if any)
CNTL
2FH = Initiates a Connect Request (SABM)
43H = Initiates a Disconnect Request (DISC)
63H = Acknowledges a Connect or Disconnect (UA)
0FH = Disconnected Mode Status Response (DM)
87H = Frame Reject Status Response (FRMR)
03H = Broadcast Information Packet (UI)

The Poll/Final (P/F) bit, 10H, is used to force a response from the receiving station. Used here and in other frame types for this function.

PID - Protocol ID for frames containing text (see I-Frames)

TEXT - Text field information, only for broadcast packets

Supervisory Frames:

FLAG DC SC RC CNTL FCS1 FCS2 FLAG

DC etc. - Address fields, as above

CNTL

-7 -6 -5 -4 ----3 --2 --1 --0
---------------------------------
] - Nr - ]P/F] - 0 - 0 - 0 - 1 ] Receive Ready
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] - Nr - ]P/F] - 0 - 1 - 0 - 1 ] Rcv Not Ready
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] - Nr - ]P/F] - 1 - 0 - 0 - 1 ] Reject
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Nr = Sequence count of next expected I-frame
P/F = Poll/Final bit

Information Frames:

FLAG DC SC RC CNTL PID TEXT ... TEXT FCS1 FCS2 FLAG

DC etc. - Address fields, as above

CNTL

-7 -6 -5 -4 ----3 --2 --1 --0
---------------------------------
] -- Nr -- ]P/F] ---- Ns --- ]0] I-frame
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Nr = Sequence count of next expected I-frame
P/F = Poll/Final bit
Ns = Sequence count of this I-frame

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