Kawasaki 80C152 - Manual (Page 53)

KS152JB Universal Communications Controller
Technical Specifications
Kawasaki LSI USA, Inc. Page 53 of 120 Ver. 0.9 KS152JB2
count must be done by the user software. The Hardware Based Acknowledge option that is pro-
vided in the C152 is not compatible with standard SDLC protocol.
3.3.8 PRIMARY/SECONDARY STATIONS
All SDLC networks are based upon a primary/secondary station relationship. There can be only
one primary station in a network and all the other stations are considered secondary. All commu-
nication is between the primary and secondary station. Secondary station to secondary station
direct communication is prohibited. If there is a need for secondary to secondary communication,
the user software will have to make allowances for the master to act as an intermediary. Secondary
stations are allowed use of the serial line only when the master permits them. This is done by the
master polling the secondary stations to see if they have a need to access the serial line. This
should prevent any collisions from occurring, provided each secondary station has its own unique
address. This arrangement also partially determines the types of networks supported. Normally
SDLC networks consists of point-to-point, multi-drop, or ring configurations and the C152 sup-
ports all of these. However, some SDLC processors support an automatic one bit delay at each
node that is not supported by the C152. In a “Loop Mode” configuration, is necessary that the
transmission be delayed from the reception of the frames from the upstream station before passing
the message to the downstream station. This delay is necessary so that a station can decode its
own address before the message is passed on. The various networks are shown in Figure.
Multi-Drop Network
Point-to-point Network
PRIMARY
SECONDARY
PRIMARY
SECONDARY SECONDARY SECONDARY
Ring Network
SECONDARY
PRIMARY
SECONDARY
SECONDARY