Image Processing Reference
In-Depth Information
own set of parameters. These are independent of the parameters of the controller, although both
parameter sets represent the same communication cycle and slot pattern. During runtime, the BG
receives synchronization signals from the controller in order to keep track with the communication
cycle. Using its own clock the BG verifies those synchronization signals due to avoid being influenced
by a faulty controller.
Typically, the BG will be combined with the transceiver component. Optionally, a central BG
located inside a star coupler can be used.
16.3.6 Protocol Services
Application information is transmitted by the CC inside of frames. A frame contains one or more
application signals. A controller provides an interface for frame transmission and reception that con-
sists of buffers. A buffer consists of a control/status section and the data section. hese sections have
different semantics for receive and transmit frames and for static and dynamic slots.
The control section of transmit buffers for frames in the static segment contains the slot ID and
the channel, in which the frame is transmitted. Once a buffer of this type is configured and the com-
munication is started, the controller periodically transmits the data in the data section in the slot
configured in the slot ID. When the application changes the data in the buffer, the subsequent trans-
mission contains the new data. A special control flag allows modifying this behavior such that in case
the application does not update the data in the buffer, a null frame is transmitted, signaling the failure
to update other controllers. The control section of a receive buffer for frames in the static segment
deinestheslotIDandthechannelfromwhichtheframeshouldbeloadedintothebufer.hestatus
section contains the frame receive status and the null frame indicator. One special flag indicates that
a new frame has been received. It is important to note that the slot ID and the channel selection for
slotsinthestaticsegmentcannotbechangedduringoperation.
Buferstatusandcontrolsectionforframesinthedynamicsegmentaresimilartothebufersin
the static segment. Differences result from the fact that the slot ID and the channel can be changed
during normal operation and that multiple buffers can be grouped together to form a FIFO for frame
reception from the dynamic section.
The CC provides a set of timers that run clocked by the synchronized time of the network. Several
different conditions can be used to generate interrupts based on these timers. These interrupts are
efficient means to synchronize the application with the timing on the bus.
16.3.7 FlexRay Current State
By the end of , the first FlexRay series application was introduced in a car, proving the readiness
for series application of the technology. Two further applications are scheduled for start of production
in and in premium cars. In , five silicon vendors provide microcontrollers with
FlexRay interfaces in and bit architectures. Four silicon vendors provide physical layer chips.
The current version of the protocol specification is . rev A. As a result of the experience gained
from the first series projects, the FlexRay Consortium continues to improve the FlexRay specifica-
tion. These improvements focus on single channel version, standardization of the . and Mbit
transmission rate and a time-triggered master mode for the clock synchronization.
16.4 System Configuration
With the advent of the TDMA communication technologies and especially in the automotive
application domain, the off-line configuration of networks gets increasingly important. Off-line
