M32C80 Datasheet, PDF (218/352 Pages) Renesas Technology Corp – 16/32-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M32C/80 SERIES

M32C/80 Group
16. Serial I/O (Special Function)
16.3.6 SDA Input
When the IICM2 bit in the UiSMR2 register (i=0 to 4) is set to "0", the first eight bits of received data are
stored into bits 7 to 0 (D7 to D0) in the UiRB register. The ninth bit (D8) is ACK or NACK.
When the IICM2 bit is set to "1", the first seven bits (D7 to D1) of received data are stored into bits 6 to 0
in the UiRB register. Store the eighth bit (D0) into bit 8 in the UiRB register.
If the IICM2 bit is set to "1" and the CKPH bit in the UiSMR3 register is set to "1", the same data as that of
when setting the IICM2 bit to "0" can be read. To read the data, read the UiRB register after the rising
edge of the ninth bit of the transfer clock.
16.3.7 ACK, NACK
When the STSPSEL bit in the UiSMR4 register (i=0 to 4) is set to "0" (serial I/O circuit selected) and the
ACKC bit in the UiSMR4 register is set to "1" (ACK data output), the SDAi pin provides the value output
set in the ACKD bit in the UiSMR4 register.
If the IICM2 bit is set to "0", the NACK interrupt request is generated when the SDAi pin is held high ("H")
on the rising edge of the ninth bit of the transfer clock. The ACK interrupt request is generated when the
SDAi pin is held low ("L") on the rising edge of the ninth bit of the transfer clock.
When ACK is selected to generate a DMA request, the DMA transfer is activated by an ACK detection.
16.3.8 Transmit and Receive Reset
When the STC bit in the UiSMR2 register (i=0 to 4) is set to "1" (UARTi initialization enabled) and a start
condition is detected,
- the transmit shift register is reset and the content of the UiTB register is transferred to the transmit shift
register. The first bit starts transmitting when the next clock is input. UARTi output value remains
unchanged between when the clock is applied and when the first bit data output is provided. The value
remains the same as when start condition was detected.
- the receive shift register is reset and the first bit start receiving when the next clock is applied.
- the SWC bit is set to "1" (SCL wait output enabled). The SCLi pin becomes "L" on the falling edge of the
ninth bit of the transfer clock.
If UARTi transmission and reception are started with this function, the TI bit in the UiC1 register remains
unchanged. Select the external clock as the transfer clock when using this function.
Rev. 1.00 Nov. 01, 2005 Page 199 of 330
REJ09B0271-0100