![](http://datasheet.mmic.net.cn/30000/M30280M8V-XXXHP_datasheet_2358818/M30280M8V-XXXHP_226.png)
14. Serial I/O
page 206
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Figure 14.36 S3C and S4C Registers, S3BRG and S4BRG Registers, and S3TRR and S4TRR Registers
b7
b0
Symbol
Address
After Reset
S3BRG
036316
Undefined
S4BRG
036716
Undefined
0016 to FF16
b7
b0
Symbol
Address
After Reset
S3TRR
036016
Undefined
S4TRR
036416
Undefined
SymbolAddressAfter Reset
S3C036216
010000002
S4C036616
010000002
b7b6b5b4b3b2b1b0
RW
Function
SMi5
SMi1
SMi0
SMi3
SMi6
SMi7
Internal synchronous clock
select bit
Transfer direction select bit
S I/Oi port select bit
SOUTi initial value set bit
0 0 : Selecting f1 or f2
0 1 : Selecting f8
1 0 : Selecting f32
1 1 : Do not set
b1 b0
0 : External clock (2)
1 : Internal clock (3)
Effective when the SMi3 is set to 0
0 : “L” output
1 : “H” output
0 : Input/output port
1 : SOUTi output, CLKi function
Bit Name
Bit
Symbol
Synchronous clock select bit
0 : LSB first
1 : MSB first
SMi2SOUTi output disable bit0 : SOUTi output
1 : SOUTi output disable(high impedance)
SMi4CLK polarity selct bit
0 : Transmit data is output at falling edge of
transfer clock and receive data is input at
rising edge
1 : Transmit data is output at rising edge of
transfer clock and receive data is input at
falling edge
RW
WO
(4)
(5)
NOTES:
1. Set the S4C register by the next instruction after setting the PRC2 bit in the PRCR register to 1 (write enable).
2. Set the SMi3 bit to 1 and the corresponding port direction bit to 0 (input mode).
3. Set the SMi3 bit to 1 (SOUTi output, CLKi function) .
4. When the SMi2 bit is set to 1, the corresponding pin goes to high-impedance regardless of the function in use.
5. When the SMi1 and SMi0 bit settings are changed, set the SiBRG register .
NOTES:
1. Write to this register while serial I/O is neither transmitting or receiving.
2. To receive data, set the corresponding port direction bit for SINi to 0 (input mode).
NOTES:
1. Write to this register while serial I/O is neither transmitting or receiving.
2. Use MOV instruction to write to this register.
3. Set the SiBRG register after setting bits SMi1 and SMi0 in the SiC register.
Transmission/reception starts by writing transmit data to this register. After
transmission/reception completion, reception data can be read by reading this register.
Assuming that set value = n, BRGi divides the count source by
n + 1
Setting Range
Description
SI/Oi Control Register (i = 3, 4) (1)
SI/Oi Bit Rate Generation Register (i = 3, 4) (1, 2, 3)
SI/Oi Transmit/Receive Register (i = 3, 4) (1, 2)