SH7261 datasheet(758/1348 Pages) RENESAS

758 / 1348 page

Section 16 Serial Communication Interface with FIFO (SCIF)

Rev. 2.00 Sep. 07, 2007 Page 726 of 1312

REJ09B0320-0200

16.6

Usage Notes

Note the following when using the SCIF.

16.6.1

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 TTRG1 and TTRG0 in the FIFO control register (SCFCR). After TDFE 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

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).

16.6.2

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 RTRG1 and RTRG0 in the FIFO control register (SCFCR). After RDF 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. RDF 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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