SH7760 Datasheet, PDF (647/1345 Pages) Renesas Technology Corp – SuperHTM RISC engine

Table 17.7 SCIF Interrupt Sources
Interrupt
Source Description
DMAC
Activation
Priority on
Reset Release
ERI
Interrupt initiated by receive error flag (ER)
Not possible
High
RXI
Interrupt initiated by receive FIFO data full flag Possible
(RDF) or receive data ready flag (DR)*
BRI
Interrupt initiated by break flag (BRK) or overrun Not possible
error flag (ORER)
TXI
Interrupt initiated by transmit FIFO data empty Possible
flag (TDFE)
Low
Note: *An RXI interrupt by setting of the DR flag is available only in asynchronous mode.
17.6 Usage Notes
Note the following when using the SCIF.
(1) SCFTDR Writing and the TDFE Flag
The TDFE flag in SCFSR is set when the number of transmit data bytes written in SCFTDR
has fallen to or below the transmit trigger number set by bits TTRG1 and TTRG0 in 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, even 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 SCTFDR.
(2) SCFRDR Reading and the RDF Flag
The RDF flag in SCFSR is set when the number of receive data bytes in SCFRDR has become
equal to or greater than the receive trigger number set by bits RTRG1 and RTRG0 in 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 read in SCFRDR is equal to or greater than the trigger
number, the RDF flag will be set to 1 again even if it is cleared to 0. After the receive data is
read, clear the RDF flag readout to 0 in order to reduce the number of data bytes in SCFRDR
to less than the trigger number.
The number of receive data bytes in SCFRDR can be found from SCRFDR.
Rev. 1.0, 02/03, page 597 of 1294