R5F72115D160FPV datasheet(745/1228 Pages) RENESAS

745 / 1228 page

Section 15 Serial Communication Interface with FIFO (SCIF)

Rev. 2.00 May. 08, 2008 Page 721 of 1200

REJ09B0344-0200

15.6

Usage Notes

Note the following when using the SCIF.

15.6.1

SCFTDR Writing and TDFE Flag

The TDFE flag in the serial status register (SCFSR) is set when the number of transmit data bytes

written in the transmit FIFO data register (SCFTDR) has fallen below the transmit trigger number

set by bits TTRG[1:0] in the FIFO control register (SCFCR). After the TDFE flag is set, transmit

data up to the number of empty bytes in SCFTDR can be written, allowing efficient continuous

transmission.

However, if the number of data bytes written in SCFTDR is equal to or less than the transmit

trigger number, the TDFE flag will be set to 1 again after being read as 1 and cleared to 0. TDFE

flag clearing should therefore be carried out when SCFTDR contains more than the transmit

trigger number of transmit data bytes.

The number of transmit data bytes in SCFTDR can be found from the upper 8 bits of the FIFO

data count register (SCFDR).

15.6.2

SCFRDR Reading and RDF Flag

The RDF flag in the serial status register (SCFSR) is set when the number of receive data bytes in

the receive FIFO data register (SCFRDR) has become equal to or greater than the receive trigger

number set by bits RTRG[1:0] in the FIFO control register (SCFCR). After RDF flag is set,

receive data equivalent to the trigger number can be read from SCFRDR, allowing efficient

continuous reception.

However, if the number of data bytes in SCFRDR exceeds the trigger number, the RDF flag will

be set to 1 again if it is cleared to 0. The RDF flag should therefore be cleared to 0 after being read

as 1 after reading the number of the received data in the receive FIFO data register (SCFRDR)

which is less than the trigger number.

The number of receive data bytes in SCFRDR can be found from the lower 8 bits of the FIFO data

count register (SCFDR).

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