Advanced Data Communication Control Procedures

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.[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.[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,[3] ADCCP specifies a 2-byte control field format with the P/F flag duplicated.[4] Later HDLC specifications, in particular ISO/IEC 13239, changed that to specify that U frames have 1-byte control fields in all cases.

ADCCP control fields

First byte								Second byte								Description
0	1	2	3	4	5	6	7	0	1	2	3	4	5	6	7
0	N(S)			P/F	N(R)											I frame, N(S) is a 3-bit send sequence number
1	0	type		P/F	N(R)											S frame, N(R) is a 3-bit receive sequence number
1	1	type		P/F	type											U frame
0	N(S)							P/F	N(R)							Extended I frame, N(S) is a 7-bit sequence number
1	0	type		—0—				P/F	N(R)							Extended S frame, N(R) is a 7-bit sequence number
1	1	type		P/F	type			P/F	—0—							Extended U frame (ADCCP only)

See also

• Data link layer
• High-Level Data Link Control
• Self-synchronizing code

References

1. Friend et al. 1988, p. 191
2. NBS 1980, p. 6, §3.0 ADCCP classes of procedures
3. ISO 1984, p. 18, §7.4 Extended control field formats
4. ANSI 1979, p. 28, §5.2.2 Extended control field

• Friend, 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.
• Guideline for implementing advanced data communication control procedures (ADCCP). National Bureau of Standards. 26 September 1980. FIPS PUB 78.
• ISO 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
• ANSI 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.