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III PERIPHERAL BLOCK: SERIAL INTERFACE
B-III-8-24 EPSON S1C33L03 FUNCTION PART
Serial Interface Interrupts and DMA
The serial interface can generate the following three types of interrupts in each channel:
• Transmit-buffer empty interrupt
• Receive-buffer full interrupt
• Receive-error interrupt
Transmit-buffer empty interrupt factor
This interrupt factor occurs when the transmit data set in the transmit data register is transferred to the shift
register, in which case the interrupt factor flag FSTXx is set to "1". At this time, if the interrupt conditions set
using the interrupt control register are met, an interrupt to the CPU is generated.
Occurrence of this interrupt factor indicates that the next transmit data can be written to the transmit data
register.
This interrupt factor can also be used to invoke IDMA, enabling transmit data to be written to the register by
means of a DMA transfer.
Receive-completion interrupt
This interrupt factor occurs when a receive operation is completed and the receive data taken into the shift
register is transferred to the receive data register, in which case the interrupt factor flag FSRXx is set to "1".
At this time, if the interrupt conditions set using the interrupt control register are met, an interrupt to the CPU
is generated. Occurrence of this interrupt factor indicates that the received data can be read out.
This interrupt factor can also be used to invoke IDMA, enabling the received data to be written into specified
memory locations by means of a DMA transfer.
Receive-error interrupt
This interrupt factor occurs when a parity, framing, or overrun error is detected during data reception, in
which case the interrupt factor flag FSERRx is set to "1". At this time, if the interrupt conditions set using the
interrupt control register are met, an interrupt to the CPU is generated.
Since all three types of errors generate the same interrupt factor, check the error flags PERx (parity error),
OERx (overrun error), and FERx (framing error) to identify the type of error that has occurred. In the clock-
synchronized mode, parity and framing errors do not occur.
Note: If a receive error (parity or framing error) occurs, the receive-error interrupt and receive-buffer full
interrupt factors occur simultaneously. However, since the receive-error interrupt has priority over
the receive-buffer full interrupt, the receive-error interrupt is processed first. It is therefore
necessary for the receive-buffer full interrupt factor flag be cleared through the use of the receive-
error interrupt processing routine.
Control registers of the interrupt controller
•Ch.0 and Ch.1
Table 8.9 shows the interrupt controller's control registers provided for each interrupt source (channel).
Table 8.9 Control Register of Interrupt Controller
Channel Interrupt factor Interrupt factor flag Interrupt enable register Interrupt priority register
Ch.0 Receive-error interrupt FSERR0(D0/0x40286) ESERR0(D0/0x40276) PSIO0[2:0](D[6:4]/0x40269)
Receive-buffer full FSRX0(D1/0x40286) ESRX0(D1/0x40276)
Transmit-buffer empty FSTX0(D2/0x40286) ESTX0(D2/0x40276)
Ch.1 Receive-error interrupt FSERR1(D3/0x40286) ESERR1(D3/0x40276) PSIO1[2:0](D[2:0]/0x4026A)
Receive-buffer full FSRX1(D4/0x40286) ESRX1(D4/0x40276)
Transmit-buffer empty FSTX1(D5/0x40286) ESTX1(D5/0x40276)
When the interrupt factor described above occurs, the corresponding interrupt factor flag is set to "1". If the
interrupt enable register bit for that interrupt factor has been set to "1", an interrupt request is generated.
Interrupts caused by an interrupt factor can be disabled by leaving the interrupt enable register bit for that
factor set to "0". The interrupt factor flag is set to "1" whenever interrupt conditions are met, regardless of the
setting of the interrupt enable register (even if it is set to "0").