AN2503 Freescale Semiconductor / Motorola, AN2503 Datasheet - Page 17

• Manufacturer Part Number: AN2503
• Description: Slave LIN Driver for the MC68HC908QT/QY Family
• Manufacturer: Freescale Semiconductor / Motorola

InitializeMsgTransmission()
Function
PutChar() Function
Sleep Mode
Functionality
Wake Up
MOTOROLA
This function initializes the transmission process. It sets all the needed
variables to the proper state, calculates the checksum for the buffer to be sent,
and points to the first element of the buffer.
This function controls the transmission flow, either terminating the transmission
(if the last byte was sent) or setting the next byte in the buffer to be sent.
Sleep mode is compatible with LIN Specification 1.2 and earlier and must be
enabled manually. When a sleep mode command is detected, the MCU will
enter low-consumption mode. The MC68HC908QY MCU uses stop mode,
which stops all activity including timers. This will reduce current consumption
from approximately 4.5 mA to less than 0.22 mA. The MCU will wake up only
with a keyboard interrupt (KBI), an external interrupt (IRQ), or a reset. In this
driver, IRQ is enabled before entering this mode and is the only way to wake
without resetting the MCU. This functionality can be implemented with or
without a transceiver.
If a transceiver is not used, the Rx pin must be tied with the IRQ pin, so that
when a 0 (dominant state) is received, IRQ will be latched and the MCU will
wake up.
If a LIN transceiver is used, there are two options:
The MCU will wake up with an external interrupt or if a reset occurs. If a reset
occurs, the complete driver will be re-initialized and information in buffers will
be lost. In case of an external interrupt, all activity will continue. IRQ will be
disabled until a new sleep mode is detected and the transceiver (if used) will be
enabled.
Slave LIN Driver for the MC68HC908QT/QY Family
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Freescale Semiconductor, Inc.
For More Information On This Product,
Use the INH functionality of the MCU connected to IRQ so that it can
wake up.
Use a voltage regulator where the INH pin is connected to a shutdown
pin in the regulator and it is turned off. After some bus activity, the
regulator will enable its voltage output and will turn the MCU on. In this
case, the MCU will be reset and proper steps must be taken to avoid
losing information.
Go to: www.freescale.com
Driver Functionality
AN2503/D
17