M16C28 Datasheet, PDF (236/423 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/Tiny SERIES

M16C/28 Group (M16C/28, M16C/28B)
14. Serial I/O
14.2.3 Functions for Setting an SOUTi Initial Value
If the SMi6 bit in SiC register is set to 0 (external clock), the SOUTi pin output level can be fixed high or low
when not transferring data. However, when transmitting data consecutively, the last bit (bit 0) value of the
last transmitted data is retained between the sccessive data transmissions. Figure 14.39 shows the
timing chart for setting an SOUTi initial value and how to set it.
(Example) When “H” selected for SOUTi initial value ⁽¹⁾
Signal written to
SiTRR register
SMi7 bit
SMi3 bit
D0
SOUTi (internal)
Port output
D0
SOUTi pin output
(i = 3, 4)
Initial value = “H” ⁽³⁾
Setting the SOUTi
initial value to “H”
(2)
Port selection switching
(I/O port SOUTi)
NOTES:
1. This diagram applies to the case where the bits in the SiC register are set as follows:
SMi2=0 (SOUTi output), SMi5=0 (LSB first) and SMi6=0 (external clock)
2. SOUTi can only be initialized when input on the CLKi pin is in the high state if the SMi4bit in the
SiC register is set to "0" (transmit data output at the falling edge of the transfer clock) or
in the low state if the SMi4 bit is set to "1" (transmit data output at the rising edge of the
transfer clock).
3. If the SMi6 bit is set to "1" (internal clock) or if the SMi2 bit is set to "1" (SOUT output disabled),
this output goes to the high-impedance state.
Setting of the initial value of SOUTi
output and starting of transmission/
reception
Set the SMi3 bit to “0”
(SOUTi pin functions as an I/O port)
Set the SMi7 bit to “1”
(SOUTi initial value = “H”)
Set the SMi3 bit to “1”
(SOUTi pin functions as SOUTi output)
“H” level is output
from the SOUTi pin
Write to the SiTRR register
Serial transmit/reception starts
Figure 14.39 SOUTi Initial Value Setting
Rev. 2.00 Jan. 31, 2007 ^{page 216} of 385
REJ09B0047-0200