FXTH87xx11 and FXTH87xx12 Embedded Firmware User Guide, Rev. 2.1
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Freescale Semiconductor, Inc.
Firmware Functions
3.2.38
void TPMS_LF_ENABLE(UINT8 u8Switch)
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Description:
Enables/disables the LFR module.
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Stack size:
5 bytes
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Approx. Duration:
32 usec
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Power Management:
This function executes entirely in RUN mode.
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Interrupt Management:
This function does not await any interrupts. It will not be affected by
interrupts.
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Resources:
LFR
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Input Parameters:
— UINT8 u8Switch: Enable (non-zero) or disable (zero) LFR.
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Returns
:
— void
3.2.39
UINT8 TPMS_LF_READ_DATA(UINT8 *u8Buffer, UINT8 u8Count)
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Description:
Once the user has configured and enabled the LFR, it is customary to go into a
low-power state mode and wait for a datagram. After the first byte of an incoming datagram is
successfully received, this function should be called immediately; It will receive the complete
datagram and place it in RAM. This function assumes that the LFR module is configured
accordingly for a Manchester reception; that the module’s interrupts are enabled; and that the first
byte has already been received and is waiting in the LFR received buffer. While waiting for the
next byte, this function goes into STOP4. If the byte, for an unexpected reason, is not received, this
function has a built-in time-out: After five continuous non-LFR interrupts, the function will assume
a failed LFR reception and exit.
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Stack size:
7 bytes
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Approx. Duration:
Data dependant; ~2 msec per byte.
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Power Management:
This function requires the core to be configured for STOP4 mode and
running at full bus speed.
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Interrupt Management:
This function utilizes the LFR interrupt to wake-up from STOP mode. It
does not await any other interrupts and should not be affected by them.
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Resources:
LFR
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Input Parameters:
— UINT8 *u8Buffer: RAM Buffer where data will be placed.
— UINT8 u8Count: Number of bytes expected.
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Returns
:
— UINT8 u8BytesReceived: Actual number of bytes received.
WARNING
This function requires ~24 usec from the moment it is called to the moment
the first byte is copied into the RAM buffer. The user must consider this time
when designing their firmware.
