Freescale Semiconductor FlexRay MFR4310 - Flexray Initialization Sequence; Number of Usable Message Buffers

To Next Page

To Previous Page

FlexRay Module (FLEXRAYV4)

MFR4310 Reference Manual, Rev. 2

Freescale Semiconductor 203

3.6.1 FlexRay Initialization Sequence

The full FlexRay module is reset with the hard reset. Additionally, the protocol engine is reset in the Stop

Mode and as a result of the RESET protocol command issued using the Protocol Operation Control

The hard reset resets all internal registers and all registers in the FlexRay module memory map. The

protocol engine reset resets only the registers in the protocol engine. All registers in memory are not reset.

The following is an initialization sequence applicable to the FlexRay module after a hard reset

1. Configure FlexRay module

— set the control bits in the Module Configuration Register (MCR)

2. Enable the FlexRay module

— set the MEN bit in the Module Configuration Register (MCR)

— the FlexRay module enters the Normal Mode

3. Configure the Protocol Engine

— write the CONFIG command into the POCCMD field of the Protocol Operation Control

— write to the PCR0, ..., PCR30 registers to set all protocol parameters.

4. Configure the Message Buffers and FIFOs

— set the number of message buffers used and the message buffer segmentation in the Message

Buffer Segment Size and Utilization Register (MBSSUTR)

— define the message buffer data size in the Message Buffer Data Size Register (MBDSR)

— configure each message buffer by setting the configuration values in the Message Buffer

Configuration, Control, Status Registers (MBCCSRn), Message Buffer Cycle Counter Filter

Registers (MBCCFRn), Message Buffer Frame ID Registers (MBFIDRn), Message Buffer

Index Registers (MBIDXRn)

— configure the receive FIFOs

5. Start the FlexRay module as a FlexRay node

— write the READY protocol command into the POCCMD field of the Protocol Operation

Control Register (POCR)

— now the FlexRay module enters the FlexRay protocol

After this sequence, the FlexRay module is configured as a FlexRay node and is ready to be integrated into

the FlexRay cluster.

3.6.2 Number of Usable Message Buffers

This section describes the relationship between the number of message buffers that can be utilized and the

required minimum CHI clock frequency.

The FlexRay module uses a sequential search algorithm to determine the individual message buffer

assigned or subscribed to the next slot. This search must be finished within one FlexRay slot. The shortest

FlexRay slot is an empty dynamic slot. An empty dynamic slot is a minislot and consists of gdMinislot