
V PERIPHERAL MODULES 3 (INTERFACE): GENERAL-PURPOSE SERIAL INTERFACE (EFSIO)
S1C33E07 TECHNICAL MANUAL
EPSON
V-1-37
V
EFSIO
V.1.7 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
This cause of interrupt occurs when the transmit data set in the transmit data register is transferred to the shift reg-
ister, in which case the cause-of-interrupt 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 cause of interrupt
indicates that the next transmit data can be written to the transmit data register. This cause of interrupt can also be
used to invoke IDMA, enabling transmit data to be written to the register by means of a DMA transfer.
Receive-buffer full interrupt
This cause of interrupt occurs when the number of data specified with FIFOINTx[1:0] (D[6:5]/0x300Bx4) (one
data in standard mode) has been received in the receive data buffer, in which case the cause-of-interrupt 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 cause of interrupt indicates that the received data can be
read out. This cause of interrupt can also be used to invoke IDMA, enabling the received data to be written into
specified memory locations by means of a DMA transfer.
FIFOINTx[1:0]: Serial I/F Ch.x Receive Buffer Full Interrupt Timing Select Bits in the Serial I/F Ch.x IrDA
Register (D[6:5]/0x300Bx4)
Receive-error interrupt
This cause of interrupt occurs when a parity, framing, or overrun error is detected during data reception, or
when a transmit error is detected during data transmission in ISO7816 T = 0 mode, in which case the cause-of-
interrupt 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 four types of errors generate the same cause of interrupt, check the error flags PERx (parity error),
OERx (overrun error), FERx (framing error), and TER1 (transmit error flag) to identify the type of error that
has occurred. In the clock-synchronized mode, parity and framing errors do not occur.
PERx: Serial I/F Ch.x Parity Error Flag in the Serial I/F Ch.x Status Register (D3/0x300Bx2)
OERx: Serial I/F Ch.x Overrun Error Flag in the Serial I/F Ch.x Status Register (D2/0x300Bx2)
FERx: Serial I/F Ch.x Framing Error Flag in the Serial I/F Ch.x Status Register (D4/0x300Bx2)
TER1: Serial I/F Ch.1 ISO7816 Transmit Error Flag in the Serial I/F Ch.1 ISO7816 Mode Status Register
(D0/0x300B1B)
Note: If a receive error (parity or framing error) occurs, the receive-error interrupt and receive-buffer full
interrupt causes 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 neces-
sary for the receive-buffer full interrupt cause flag be cleared through the use of the receive-error
interrupt processing routine.