User`s guide

36 DC 900-1317J
ADCCP NRM Programmer’s Guide
2.6 Operational States
ADCCP link operation procedures define three fundamental states: logically discon-
nected state, initialization state, and information transfer state. Within each state,
ADCCP defines valid link operation procedures.
In the logically disconnected state, only unnumbered frames are valid. Information
frames and supervisory frames are ignored. Consequently, no information is exchanged
in this state. Link operation always starts in the logically disconnected state.
The initialization state, which is optional, can be used when support for set initializa-
tion mode (SIM) commands and request initialization mode (RIM) responses is
requested (ADCCP option 5). Link operation procedures in this state are not well
defined. This state is provided to allow implementers some freedom to initialize or
download equipment prior to starting data transfer. It allows exchange of unformatted
and unchecked bit streams.
The information transfer state allows the exchange of information and control frames.
The procedures for link operation in this state vary according to the operating mode
(NRM, ARM, or ABM) and the optional ADCCP functions selected. Within the infor-
mation state, procedures are defined for information transfer, sequence number valida-
tion, data transfer acknowledgment, and error recovery.
2.7 Optional Functions
ADCCP defines eleven optional functions. Each one affects link operation by adding or
deleting procedural requirements. These optional functions are summarized as follows:
OPTION 1 This option provides the ability to exchange station identification by
means of an unnumbered exchange identification (XID) com-
mand/response frame. Option 1 also defines an unnumbered request
disconnect (RD) response that allows a secondary station (or a sec-
ondary function in a combined station) to request the primary station