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R8C/38T-A Group
21. Clock Synchronous Serial Interface
Under development Preliminary document
Specifications in this document are tentative and subject to change.
R01UH0241EJ0010 Rev.0.10
Page 499 of 730
Aug 05, 2011
21.4.1.3
Interrupt Requests
The I2C bus interface has six interrupt requests in I2C bus interface mode and four interrupt requests in clock
Because these interrupt requests are assigned to the I2C bus interface interrupt vector table, interrupt sources
must be determined using the bits.
RE_STIE, TE_NAKIE, RIE, TEIE, TIE: Bits in SIER register
ORER_AL, STOP, NACKF, RDRF, TEND, TDRE: Bits in SISR register
When the generation conditions listed in Table 21.11 are met, an I2C bus interface interrupt request is generated. Set the interrupt generation conditions to 0 in the I2C bus interface interrupt routine.
Note that bits TDRE and TEND in the SIER register are automatically set to 0 by writing transmit data to the
SITDR register and the RDRF bit is automatically set to 0 by reading the SIRDR register. In particular, the
TDRE bit is set to 0 when transmit data is written to the SITDR register and set to 1 when data is transferred
from registers SITDR to SISDR. If the TDRE bit is further set to 0, an additional 1 byte may be transmitted.
Because the data is retained in the transmit buffer, the data is shifted to the shift register by a trigger (the TDRE
bit in the SISR register is 0), and thus the same data is retransmitted.
Also, set the RE_STIE bit in the SIER register to 1 (stop condition detection interrupt request enabled) only
when the STOP bit in the SISR register is 0.
Table 21.11
Interrupt Requests of I2C bus Interface
Interrupt Request
Generation Condition
Format
I2C bus
Clock synchronous
serial
Transmit data empty
TXI
TIE = 1 and TDRE = 1
Enabled
Transmit end
TEI
TEIE = 1 and TEND = 1
Enabled
Receive data full
RXI
RIE = 1 and RDRF = 1
Enabled
Stop condition detection
STPI
RE_STIE = 1 and STOP = 1
Enabled
Disabled
NACK detection
NAKI TE_NAKIE = 1 and ORER_AL = 1
(or TE_NAKIE = 1 and NACKF = 1)
Enabled
Disabled
Arbitration lost
Enabled
Disabled
Overrun error
Disabled
Enabled