Industrial Communication Systems

32-6 Industrial Communication Systems

32.3.3 Media Access

e Probus medium access control (MAC) includes the token-passing procedure, which is used by

complex

bus

stations

(masters)

to

communicate

with

each

other

and

the

master–slave

procedure

used

by

complex bus stations to communicate with the simple peripherals (slaves).

e

token-passing

procedure

ensures

that

the

bus

access

right

(the

token)

is

assigned

to

each

master

within

a

precisely

dened

timeframe.

e

token

message,

a

special

telegram

for

passing

the

token

from

one

master

to

the

next

master

must

be

passed

around

the

logical

token

ring

once

to

all

masters

within

a

(congurable)

ma