CP6100 Configuration and Management Manual

Overview of the CP6100 Subsystem
CP6100 Configuration and Management Manual—426741-003
2-4
Primary CP6100 Protocols
Following is a brief description of each of these protocols.
Protocol Description
ADCCP Developed by the American National Standards Institute (ANSI). The
ADCCP line protocol allows a choice of either Normal Response Mode
(NRM), Asynchronous Balanced Mode (ABM), or Asynchronous
Response Mode (ARM). Each of these ADCCP modes can have
extended control or address fields. Extended control fields allow
frames to carry larger sequence numbers, so stations can transmit
more frames before receiving an acknowledgment (see EXTENDED on
page 4-7). Larger address fields allow the support of more stations
(see the modifiers, AFLD n and ADDRESS n value on page 4-3). (A
network should have only as many stations as it has unique
addresses.) Both types of extensions affect the format of frames
exchanged over the link.
The three modes are defined as follows:
NRM In this mode, one station is configured as the primary
and the other station as the secondary. The primary
station initiates data transfer and is in control during the
exchange of messages. It notifies each secondary
station when it can transmit data and when it should
expect to receive data. The secondary station can
transmit data only when permitted to do so by the
primary station. In multipoint configurations, the
controlling station is sometimes referred to as the
supervisor and the secondary stations are referred to
as tributaries. On a point-to-point line, the primary
station polls the secondary station; on a multipoint line,
the supervisor station polls the tributaries in a
user-specified sequence.
ABM In this mode, two combined stations communicate on a
point-to-point link. A combined station is divided into
two logical substations: a primary that communicates
with the remote secondary substation, and a secondary
that communicates with the remote primary substation.
Either or both stations issue commands to set up or
dissolve the link. During data transmission, the stations
function as peers.