Motorola MPC533 Reference Manual page 682

SCI Queue Operation
receive queue, and operation continues unaffected. However, it may not be possible
to determine which data frame in the receive queue caused the noise flag to be
asserted.
• The queue is successfully filled (16 data frames) if error flags (FE and PF) are clear,
QTHF and QBHF are set, and QRPNT is reset to all zeroes.
• QOR indicates that a new data frame has been received in the data register (SC1DR),
but it cannot be placed into the receive queue due to either the QTHF or QBHF flag
being set (QSCI1SR). Under this condition, the receive queue is disabled (QRE =
0). Software may service the receive queue and clear the appropriate flag (QTHF,
QBHF). Data is not lost provided that the receive queue is re-enabled before OR
(SC1SR) is set, which occurs when a new data frame is received in the shifter but
the data register (SC1DR) is still full. The data in the shifter that generated the OR
assertion is overwritten by the next received data frame, but the data in the SC1DR
is not lost.
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PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
MPC533 Reference Manual MOTOROLA