PXD10RM Datasheet, PDF (834/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

23.2.3 Features common to LIN and UART
• Fractional baud rate generator
• 3 operating modes for power saving and configuration registers lock:
— Initialization
— Normal
— Sleep
• 2 test modes:
— Loop Back
— Self Test
• Maskable interrupts
23.3 General description
The increasing number of communication peripherals embedded on microcontrollers, for example CAN,
LIN and SPI, requires more and more CPU resources for communication management. Even a 32-bit
microcontroller is overloaded if its peripherals do not provide high-level features to autonomously handle
the communication.
Even though the LIN protocol with a maximum baud rate of 20 kbps is relatively slow, it still generates a
non-negligible load on the CPU if the LIN is implemented on a standard UART, as usually the case.
To minimize the CPU load in Master mode, LINFlex handles the LIN messages autonomously.
In Master mode, once the software has triggered the header transmission, LINFlex does not request any
software intervention until the next header transmission request in transmission mode or until the
checksum reception in reception mode.
To minimize the CPU load in Slave mode, LINFlex requires software intervention only to:
• Trigger transmission or reception or data discard depending on the identifier
• Write data into the buffer (transmission mode) or read data from the buffer (reception mode) after
checksum reception
If filter mode is activated for Slave mode, LINFlex requires software intervention only to write data into
the buffer (transmission mode) or read data from the buffer (reception mode)
The software uses the control, status and configuration registers to:
• Configure LIN parameters (for example, baud rate or mode)
• Request transmissions
• Handle receptions
• Manage interrupts
• Configure LIN error and timeout detection
• Process diagnostic information
The message buffer stores transmitted or received LIN frames.
23-2
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor