mfr4300 Freescale Semiconductor, Inc, mfr4300 Datasheet - Page 136

• Manufacturer Part Number: mfr4300
• Description: Flexray Communication Controllers
• Manufacturer: Freescale Semiconductor, Inc

FlexRay Module (FLEXRAYV2)
3.4.3.2
The receive shadow buffers are required for the frame reception process for individual message buffers.
The FlexRay module provides four receive shadow buffers, one receive shadow buffer per channel and per
message buffer segment.
Each receive shadow buffer consists of two parts, the physical message buffer located in the FRM and the
receive shadow buffer control registers located in dedicated registers. The structure of a receive shadow
buffer is shown in
Receive Shadow Buffer Index Register
The connection between the receive shadow buffer control register and the physical message buffer for the
selected receive shadow buffer is established by the receive shadow buffer index field RSBIDX in the
Receive Shadow Buffer Index Register
buffer header field in the FRM is determined according to
The length required for the message buffer data field depends on the message buffer segment that the
receive shadow buffer is assigned to. For the receive shadow buffers assigned to the first message buffer
segment, the length must be the same as for the individual message buffers assigned to the first message
buffer segment. For the receive shadow buffers assigned to the second message buffer segment, the length
must be the same as for the individual message buffers assigned to the second message buffer segment.
The receive shadow buffer assignment is described in
3.4.3.3
The receive FIFO implements a frame reception system based on the FIFO concept. The FlexRay module
provides two independent receive FIFOs, one per channel.
136
Receive Shadow Buffers
Receive FIFO
SADR_MBDF
SADR_MBHF
Figure
3-99. The four internal shadow buffer control registers can be accessed by the
SADR_MBHF = (RSBIR.RSBIDX * 10) + 0x800
Figure 3-99. Receive Shadow Buffer Structure
Frame Header
(RSBIR). The start address SADR_MBHF of the related message
(RSBIR).
>= MBDSR.MBSEG[1,2] * 2 bytes
MFR4300 Data Sheet, Rev. 3
Message Buffer Header Field
Message Buffer Data Field
Frame Data
Receive Shadow Buffer Index Register
Receive Shadow Buffer Control Register
Equation
Data Field Offset
RSBIDX_0
RSBIDX_1
RSBIDX_2
RSBIDX_3
3-3.
Slot Status
Freescale Semiconductor
(RSBIR).
Eqn. 3-3