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In telecommunications, Advanced Data Communication Control Procedures (or Protocol) (ADCCP) is a bit-oriented data link layer protocol developed by the American National Standards Institute. It is functionally equivalent to the ISO High-Level Data Link Control (HDLC) protocol.cite-ref-1[1]

Although the ISO and ANSI standards writers coordinated their work, so the differences between the standards are mainly editorial, there is one meaningful difference: ADCCP's definition of the basic subset required to implement balanced asynchronous mode includes the RSET frame, while HDLC makes it optional.cite-ref-2[2]

One major difference between the two is the unnumbered (U) format. When extended (7-bit) sequence numbers are used, I and S frames have two-byte control fields. Like early versions of HDLC,cite-ref-3[3] ADCCP specifies a 2-byte control field format with the P/F flag duplicated.cite-ref-4[4] Later HDLC specifications, in particular ISO/IEC 13239, changed that to specify that U frames have 1-byte control fields in all cases.

| First byte | First byte | First byte | First byte | First byte | First byte | First byte | First byte | Second byte | Second byte | Second byte | Second byte | Second byte | Second byte | Second byte | Second byte | Description |

|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | Description |

| 0 | N(S) | N(S) | N(S) | P/F | N(R) | N(R) | N(R) | | | | | | | | | I frame, N(S) is a 3-bit send sequence number |

| 1 | 0 | type | type | P/F | N(R) | N(R) | N(R) | | | | | | | | | S frame, N(R) is a 3-bit receive sequence number |

| 1 | 1 | type | type | P/F | type | type | type | | | | | | | | | U frame |

| 0 | N(S) | N(S) | N(S) | N(S) | N(S) | N(S) | N(S) | P/F | N(R) | N(R) | N(R) | N(R) | N(R) | N(R) | N(R) | Extended I frame, N(S) is a 7-bit sequence number |

| 1 | 0 | type | type | —0— | —0— | —0— | —0— | P/F | N(R) | N(R) | N(R) | N(R) | N(R) | N(R) | N(R) | Extended S frame, N(R) is a 7-bit sequence number |

| 1 | 1 | type | type | P/F | type | type | type | P/F | —0— | —0— | —0— | —0— | —0— | —0— | —0— | Extended U frame (ADCCP only) |

• See also

• References

• Data link layer

• High-Level Data Link Control

• Self-synchronizing code

cite-note-11. ↑ Friend et al. 1988, p. 191

cite-note-22. ↑ NBS 1980, p. 6, §3.0 ADCCP classes of procedures

cite-note-33. ↑ ISO 1984, p. 18, §7.4 Extended control field formats

cite-note-44. ↑ ANSI 1979, p. 28, §5.2.2 Extended control field

• citereffriendfikebakerbellamy1988Friend, George E.; Fike, John L.; Baker, H. Charles; Bellamy, John C. (1988). Understanding Data Communications (2nd ed.). Indianapolis: Howard W. Sams & Company. ISBN 0-672-27270-9.

• citerefnbs1980Guideline for implementing advanced data communication control procedures (ADCCP). National Bureau of Standards. 26 September 1980. FIPS PUB 78.

• citerefiso1984ISO 4335:1984 Data Communication—High Level Data Link Control Procedures—Consolidation of Elements of Procedures (PDF). Archived (PDF) from the original on 23 March 2019. Alt URL

• citerefansi1979ANSI X3.66-1979: American National Standard for advanced data communication procedures (ADCCP). American National Standards Institute. 9 January 1979. FIPS PUB 71-1980.

• This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22.