12 UART (UART3)
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
12-9
TECHNICAL MANUAL (Rev. 1.0)
12.6.3 Overrun Error
If the receive data buffer is still full (two bytes of received data have not been read) when a data reception to the
shift register has completed, an overrun error occurs as the data cannot be transferred to the receive data buffer.
When an overrun error occurs, the UA
n
INTF.OEIF bit (overrun error interrupt flag) is set to 1.
12.7 Interrupts
The UART3 has a function to generate the interrupts shown in Table 12.7.1.
Table 12.7.1 UART3 Interrupt Function
Interrupt
Interrupt flag
Set condition
Clear condition
End of transmission
UAnINTF.TENDIF When the UAnINTF.TBEIF bit = 1 after
the stop bit has been sent
Writing 1 or software reset
Framing error
UAnINTF.FEIF
Refer to the “Receive Errors.”
Writing 1, reading received
data that encountered an
error, or software reset
Parity error
UAnINTF.PEIF
Refer to the “Receive Errors.”
Writing 1, reading received
data that encountered an
error, or software reset
Overrun error
UAnINTF.OEIF
Refer to the “Receive Errors.”
Writing 1 or software reset
Receive buffer two bytes full UAnINTF.RB2FIF When the second received data byte is
loaded to the receive data buffer in which
the first byte is already received
Reading received data or
software reset
Receive buffer one byte full UAnINTF.RB1FIF When the first received data byte is load-
ed to the emptied receive data buffer
Reading data to empty
the receive data buffer or
software reset
Transmit buffer empty
UAnINTF.TBEIF When transmit data written to the trans-
mit data buffer is transferred to the shift
register
Writing transmit data
The UART3 provides interrupt enable bits corresponding to each interrupt flag. An interrupt request is sent to the
interrupt controller only when the interrupt flag, of which interrupt has been enabled by the interrupt enable bit, is
set. For more information on interrupt control, refer to the “Interrupt Controller” chapter.
12.8 Control Registers
UART3 Ch.
n
Clock Control Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
UAnCLK
15–9 –
0x00
–
R
–
8
DBRUN
0
H0
R/W
7–6 –
0x0
–
R
5–4 CLKDIV[1:0]
0x0
H0
R/W
3–2 –
0x0
–
R
1–0 CLKSRC[1:0]
0x0
H0
R/W
Bits 15–9 Reserved
Bit 8
DBRUN
This bit sets whether the UART3 operating clock is supplied in DEBUG mode or not.
1 (R/W): Clock supplied in DEBUG mode
0 (R/W): No clock supplied in DEBUG mode
Bits 7–6
Reserved
Bits 5–4
CLKDIV[1:0]
These bits select the division ratio of the UART3 operating clock.
Bits 3–2
Reserved