6100 ADCCP Programming Manual

1 Introduction to 6100 ADCCP
069225 Tandem Computers Incorporated 1–1
ADCCP is a bit-synchronous data communications line protocol developed by the
American National Standards Institute (ANSI). It is defined in ANSI Standard X3.66-
1979, “Advanced Data Communication Control Procedures.” ADCCP is a superset of
the high-level data link control (HDLC) and synchronous data link control (SDLC)
protocols.
The ANSI definition of ADCCP allows for:
Control of a single point-to-point or multipoint data link
Two-way alternate (TWA) or two-way simultaneous (TWS) transmission
Use of leased or switched facilities
ADCCP features include:
Choice of line control mode
Normal Response Mode (NRM)
Asynchronous Balanced Mode (ABM)
Asynchronous Response Mode (ARM)
Data code transparency
Multiple frame transmission before acknowledgment
Cyclic Redundancy Checking (CRC)
Standard or extended address fields
Standard or extended control fields
Features of the 6100
ADCCP Product
The ADCCP protocol module runs in a line interface unit (LIU) on a 3650/6100 or
communications subsystem (CSS) or a 3605/6105 communications controller. The LIU
consists of a communications line interface processor (CLIP) and a line interface
module (LIM). The protocol module is downloaded to the CLIP of the LIU from a disk
file either when the system is cold-loaded or by operator request. A single copy of
ADCCP controls one data communication line.
To use the line controlled by ADCCP, applications make file-management requests,
such as OPEN, READ, or WRITE. These requests are handled by the I/O process,
while other tasks are handled by requests to the protocol module. Requests to the
protocol module are encoded in WRITEREAD calls. The “write” part of the call
delivers the request to the LIU. The “read” part carries the response message back to
the application. Table 1-1 lists the requests an application can make to the ADCCP
protocol module.