R01UH0092EJ0110 Rev.1.10
Page 528 of 807
Jul 31, 2012
M16C/64C Group
24. Serial Interface SI/O3 and SI/O4
24.3.4
Internal Clock
When the SMi6 bit in the SiC register is 1, data is transmitted/received using the internal clock. The
internal clock is selected by setting the PCLK1 bit in the PCLKR register and bits SMi1 to SMi0 in the
SiC register. When using f1 as the clock source of the internal clock, set the PCKSTP1A bit in the
PCLKSTP1 register to 0 (f1 provide enabled).
When the internal clock is used as the transmit/receive clock, the SOUTi pin becomes high-impedance
from when the SMi3 bit in the SiC register is set to 1 (SI/Oi enabled) and the SMi2 bit is set to 0 (SOUTi
output enabled) to when the first data is output.
When writing transmit data to the SiTRR register, data transmission/reception starts by outputting the
transmit/receive clock from the CLKi pin after waiting between 0.5 to 1.0 cycles of the transmit/receive
clock. After 8 bits of data have been transmitted/received, the transmit/receive clock from the CLKi pin
stops.
Figure 24.4 shows SI/Oi Operation Timing (Internal Clock).
Figure 24.4
SI/Oi Operation Timing (Internal Clock)
D0
D1
D2
D3
D4
D5
D6
CLKi output
SOUTi output
SINi input
Write signal to the
SiTRR register
The above diagram assumes the following:
In the SiC register, SMi2 = 0 (SOUTi output), SMi3 = 1 (SOUTi output, CLKi function), SMi4 = 0 (transmit data is output at
a falling edge of the transmit/receive clock, and receive data is input at a rising edge), SMi5 = 0 (LSB first), SMi6 = 1
(internal clock).
In the S34C2 register, the SM26 bit (SOUT3) or SM27 bit (SOUT4) = 0 (high-impedance after transmission).
SI/Oi internal clock
IR bit in the SiIC
register
i = 3, 4
D7
D7
D0
D1
D2
D3
D4
D5
D6
Transmission/reception starts after waiting between 0.5 to 1.0 cycles of
transmit/receive clock by writing to the SiTRR register.
Hi-Z
Hi-Z
Содержание M16C Series
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