14 I
2
C (I2C)
14-16
Seiko Epson Corporation
S1C17M20/M21/M22/M23/M24/M25
TECHNICAL MANUAL (Rev. 1.0)
14.5 Interrupts
The I2C has a function to generate the interrupts shown in Table 14.5.1.
Table 14.5.1 I2C Interrupt Function
Interrupt
Interrupt flag
Set condition
Clear condition
End of data
transfer
I2CnINTF.BYTEENDIF When eight-bit data transfer and the following ACK/
NACK transfer are completed
Writing 1,
software reset
General call
address reception
I2CnINTF.GCIF
Slave mode only: When the general call address is
received
Writing 1,
software reset
NACK reception I2CnINTF.NACKIF
When a NACK is received
Writing 1,
software reset
STOP condition I2CnINTF. STOPIF
Master mode: When a STOP condition is gener-
ated and the bus free time (t
BUF
) between STOP and
START conditions has elapsed
Slave mode: When a STOP condition is detected
while the I2C Ch.n is selected as the slave currently
accessed
Writing 1,
software reset
START condition I2CnINTF. STARTIF
Master mode: When a START condition is issued
Slave mode: When an address match is detected
(including general call)
Writing 1,
software reset
Error detection
I2CnINTF. ERRIF
Refer to “Error Detection.”
Writing 1,
software reset
Receive buffer full I2CnINTF. RBFIF
When received data is loaded to the receive data
buffer
Reading received
data (to empty the
receive data buffer),
software reset
Transmit buffer
empty
I2CnINTF. TBEIF
Master mode: When a START condition is issued or
when an ACK is received from the slave
Slave mode: When transmit data written to the
transmit data buffer is transferred to the shift regis-
ter or when an address match is detected with R/W
bit set to 1
Writing transmit data
The I2C provides interrupt enable bits corresponding to each interrupt flag. An interrupt request is sent to the inter-
rupt 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.
(1) START condition interrupt
Master mode
SDA
SCL
BRT + 3
f
CLK_I2Cn
TXSTART = 0
STARTIF = 1
TXSTART = 1
Slave mode
Address matching the I2CnOADR register
SDA
SCL
1
2
7
8
R/W
ACK
9
TR = 0/1 STARTIF = 1
BSY = 1