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Application information
46.9.3.1 Overrun operation
The assertion of S1[OR] indicates that a significant event has occurred. The assertion
indicates that received data has been lost because there was a lack of room to store it in
the data buffer. Therefore, while S1[OR] is set, no further data is stored in the data buffer
until S1[OR] is cleared. This ensures that the application will be able to handle the
overrun condition.
In most applications, because the total amount of lost data is known, the application will
attempt to return the system to a known state. Before S1[OR] is cleared, all received data
will be dropped. For this, the software does the following.
1. Remove data from the receive data buffer. This could be done by reading data from
the data buffer and processing it if the data in the FIFO was still valuable when the
overrun event occurred, or using CFIFO[RXFLUSH] to clear the buffer.
2. Clear S1[OR]. Note that if data was cleared using CFIFO[RXFLUSH], then clearing
S1[OR] will result in SFIFO[RXUF] asserting. This is because the only way to clear
S1[OR] requires reading additional information from the FIFO. Care should be taken
to disable the SFIFO[RXUF] interrupt prior to clearing the OR flag and then clearing
SFIFO[RXUF] after the OR flag has been cleared.
When LIN break detect (LBKDE) is asserted, S1[OR] has significantly different behavior
than in other modes. S1[OR] will be set, regardless of how much space is actually
available in the data buffer, if a LIN break character has been detected and the
corresponding flag, S2[LBKDIF], is not cleared before the first data character is received
after S2[LBKDIF] asserted. This behavior is intended to allow the software sufficient
time to read the LIN break character from the data buffer to ensure that a break character
was actually detected. The checking of the break character was used on some older
implementations and is therefore supported for legacy reasons. Applications that do not
require this checking can simply clear S2[LBKDIF] without checking the stored value to
ensure it is a break character.
46.9.4 Match address registers
The two match address registers allow a second match address function for a broadcast or
general call address to the serial bus, as an example.
46.9.5 Modem feature
This section describes the modem features.
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KV4x Reference Manual, Rev. 2, 02/2015
Preliminary
Freescale Semiconductor, Inc.
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