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CHAPTER 3 FUNCTIONAL DESCRIPTION
User’s Manual S14054EJ4V0UM
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(c) Appending status information
The
µ
PD98431 can append the status information of a packet to the receive data stream that is read from the
FIFO bus. When the APSS bit of the MACC3 register is set to 1, the status information on the packet to be
read is prefixed to the receive data stream. If the APSE bit of the MACC3 register is set to 1, the status
information is suffixed to the receive data stream. The status information that is appended is the contents of
the RSVREG register that are updated each time a packet has been received. These contents are
appended as 32-bit data.
(3) Timing for changing access direction of FIFO bus in 64-bit single bus mode
Figure 3-11 shows the timing for switching between reading receive data and writing transmit data in the 64-bit
single bus mode. Be sure to deassert the FEN# signal once before switching the operation from reading to
writing or vice versa.
If the FEN# signal is deasserted during a write operation, detection of deasserting the FEN# signal to the next
rising edge of FCLK is assumed as valid writing.
If the FEN# signal is deasserted during a read operation, the valid data is output after detection of deasserting
the FEN# signal until the FCLK rises the next time. If the data read last after the FEN# signal has been
deasserted is the intermediate data of the packet being read, however, the internal operation of the chip to read
data from the receive FIFO is not stopped by deasserting the FEN# signal. Consequently, the rest of the data
cannot be correctly read when reading is resumed. To avoid this, confirm the end of data by completely reading
the packet before deasserting the FEN# signal, or input the SKIP signal to set the FIFO bus in IDLE status and
then deassert the FEN# signal.