Enhanced Serial Communication Interface (eSCI)
26-46
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
Figure 26-40. DMA Controlled LIN TX Frame generation
26.4.6.4
LIN RX frame generation
The eSCI module supports two modes of LIN RX Frame generation and reception, the CPU controlled
mode and the DMA controlled mode. In the CPU controlled mode, the application provides the required
data by subsequent CPU write accesses to the
LIN Transmit Register (eSCI_LTR)
received data by subsequent CPU read accesses to the
LIN Receive Register (eSCI_LRR)
. In the DMA
controlled mode, the DMA controller provides the required frame configuration data in response to DMA
requests generated by the eSCI module and transfers the received frame data to the memory in response to
DMA requests generated by the eSCI module.
26.4.6.4.1
CPU Controlled LIN RX Frames generation
In this mode, the application initiates the generation of an LIN RX Frame by a sequence of subsequent
CPU write accesses to the
LIN Transmit Register (eSCI_LTR)
. When the eSCI module has processed the
data written into
LIN Transmit Register (eSCI_LTR)
, the TXRDY interrupt flag in the
Status Register 2 (eSCI_IFSR2)
will be set.
The application should clear the TXRDY interrupt flag
before
writing data into the
because the eSCI module will set the TXRDY one clock cycle after the write access.
The first data written to the
LIN Transmit Register (eSCI_LTR)
provides the Identifier and Identifier Parity
fields. The second data written defines the number of data bytes requested from the LIN slave. The third
data written defines the CRC and checksum generation. The TD bit has to set to 0 to invoke the RX frame
generation. The TO field defines the upper part of the timeout value. The fourth byte written defines the
lower part of the timeout value.
After the fourth byte was written the generation of a LIN RX frame is started. Firstly, a break field is
transmitted, then the synch field and the protected identifier field. After the transmission of the protected
identifier, the eSCI module starts to receive the frame data transmitted by the LIN slave. When the module
has received a complete byte field, the received data are transferred into the
DMA
Controller
eSCI
CSM
TX DMA
channel
ID[5:0]
P[1:0]
LEN
1
CSE CRC TD
2
0
DATA 1
DATA 2
DATA N
System Memory
1
LEN must be set to N
2
TD must be set to 1
Break
Synch
Identifier
DATA 1
DATA N
Checksum
LIN TX frame
Summary of Contents for PXR4030
Page 1: ...PXR40 Microcontroller Reference Manual Devices Supported PXR4030 PXR4040 PXR40RM Rev 1 06 2011...
Page 30: ...PXR40 Microcontroller Reference Manual Rev 1 Freescale Semiconductor xxx...
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Page 120: ...Signal Descriptions 3 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
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