FlexRay Communication Technology - Networked Embedded Systems - page 386

Node

Host

Host interface

CC

Bus guardian

BD

Channel 0
Channel 1

FIGURE . ECU architecture.

16.3.1 Media Access
he media access strategy of FlexRay is basically a TDMA scheme with some very specific properties.
The basic element of the TDMA scheme is a communication cycle. A communication cycle contains
a static segment, a dynamic segment, and two protocol segments called symbol window and network
idle time (Figure .). Communication cycles are executed periodically from start-up of the network
until shutdown. Two or more communication cycles can form an application cycle.
The static segment consists of slots with fixed duration. The duration and the number of slots are
determined by configuration parameters of the FlexRay controllers. hese parameters must be identi-
calinallcontrollersofanetwork.heyformaso-calledglobalcontract.Eachslotisexclusivelyowned

Communication cycle

Network idle time

Network communication time

Static segment Dynamic segment Symbol window

Optional

Minislot Minislot Minislot Minislot Minislot Minislot

Static slot Static slot Static slot

FIGURE . FlexRay communication cycle.