PXD20RM Datasheet, PDF (966/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

27.7.2.1 Data transmission (transceiver as publisher)
When LINFlexD receives the identifier, an RX interrupt is generated. The software must:
• Read the received ID in the BIDR register
• Fill the BDR registers
• Specify the data field length using the BIDR[DFL] field
• Trigger the data transmission by setting LINCR2[DTRQ]
One or several identifier filters can be configured for transmission by setting the DIR bits in the
corresponding IFCR registers and activated by setting one or several bits in the IFER register.
When at least one identifier filter is configured in transmission and activated, and if the received ID
matches the filter, a specific TX interrupt is generated.
Typically, the software has to copy the data from RAM locations to the BDRL and BDRM registers. To
copy the data to the right location, the software has to identify the data by means of the identifier. To avoid
this and to ease the access to the RAM locations, the LINFlexD controller provides a Filter Match Index.
This index value is the number of the filter which matched the received identifier.
The software can use the index in the IFMI register to directly access the pointer which points to the right
data array in the RAM area and copy this data to the BDRL and BDRM registers (see Figure 27-10).
Using a filter avoids the software having to configure the direction, the data field length and the checksum
type in the BDIR register. The software fills the BDRL and BDRM registers and triggers the data
transmission by setting LINCR2[DTRQ].
If LINFlexD cannot provide enough TX identifier filters to handle all identifiers the software has to
transmit data for, then a filter can be configured in mask mode (refer to Section 27.7.3, Slave mode with
identifier filtering) in order to manage several identifiers with one filter only.
27.7.2.2 Data reception (transceiver as subscriber)
When LINFlexD receives the identifier, an RX interrupt is generated. The software must:
• Read the received ID in the BIDR register
• Specify the data field length using the BIDR[DFL] field before the reception of the stop bit of the
first byte of data field
When the checksum reception is completed, an RX interrupt is generated to allow the software to read the
received data in the BDR registers.
One or several identifier filters can be configured for reception by clearing the DIR bit in the corresponding
IFCR registers and activated by clearing one or several bits in the IFER register.
When at least one identifier filter is configured in reception and activated, and if the received ID matches
the filter, an RX interrupt is generated after the checksum reception only.
Typically, the software has to copy the data from the BDRL and BDRM registers to RAM locations. To
copy the data to the right location, the software has to identify the data by means of the identifier. To avoid
27-10
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor