Specifications

AN93
Rev. 0.8 153
The following two steps will allow the spurious data and bit errors to be eliminated while preserving the valid data.
1. Ignore 19 B0.
2. Use 19 B2 to discard all collected receive data.
The filtered version of the HDLC frames, based on this algorithm, is shown below with the valid data in bold.
0D 0A 43 4F 4E 4E 45 43 54 20 31 32 30 30 0D 0A 19 BE 20 20 19 B1 19 B0 19 B2 30 93
19 B1 19 B2 30 93 19 B1 19 B2 30 93 19 B1 19 B2 30 93 19 B1 19 B2 19 B2 B6 9E F7 46
19 B0 19 B2 29 C6 19 B0 19 B2 FF 98 89 18 19 B0 19 B2 92 6E EF 14 65 19 B0 19 B2 DA
BE C6 07 EA D8 31 C2 05 3C FA C8 86 C4 40 E6 19 A0 CA EA A8 F9 19 B2 8D 00 57 A5 43
29 19 B0 19 B2 05 CB 14 9F 7C 2D 19 B0 19 B2 19 B2 19 BA 0D 0A 4E 4F 20 43 41 52 52
49 45 52 0D 0A
19 B0 Followed by a data byte with > 6 mark bits in a row.
The modem looks for HDLC flags.
19 B2 HDLC Flag detected
Beginning of Packet
05 CB 14 9F 7C 2D Spurious data
19 B0 Followed by a data byte with > 6 mark bits in a row.
The modem looks for HDLC flags.
19 B2 HDLC Flag Detected
19 B2 If there is 1 bit error received in an HDLC flag, the
modem assumes a new single-byte packet. Since a 1-
byte packet is invalid, 19 B2 is generated by modem.
19 BA Loss of Carrier Detected
0D 0A 4E 4F 20 43 41 52 52 49 45 52 0D 0A NO CARRIER
Table 100. Bit Errors
Data Meaning