
CHAPTER 15 ASYNCHRONOUS SERIAL INTERFACE A (UARTA)
Preliminary User’s Manual U16541EJ1V0UM
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15.4 Control Registers
(1) UARTAn control register 0 (UAnCTL0)
The UAnCTL0 register is an 8-bit register that controls the UARTAn serial transfer operation.
This register can be read or written in 8-bit or 1-bit units.
Reset input sets this register to 10H.
Caution
Be sure to set the UAnPWR bit = 1 and the UAnRXE bit = 1 while the RXDAn pin is high level
(when UAnRDL bit of UAnOP0 register = 0).
If the UAnPWR bit = 1 and the UAnRXE bit = 1 are set while the RXDAn pin is low level,
reception will inadvertently start.
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UAnPWR
Disable operating clock operation (UARTAn reset asynchronously)
Enable operating clock operation
UAnPWR
0
1
UARTAn operation control
UAnCTL0
(n = 0 to 2)
UAnTXE UAnRXE UAnDIR
UAnPS1 UAnPS0
UAnCL
UAnSL
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3
2
1
After reset: 10H
R/W
Address: UA0CTL0 FFFFFA00H, UA1CTL0 FFFFFA10H,
UA2CTL0 FFFFFA20H
Operating clock control and UARTAn asynchronous reset are performed with the
UAnPWR bit. The TXDAn pin output is fixed to high level by setting the UAnPWR
bit to 0.
Stop transmission operation
Enable transmission operation
UAnTXE
0
1
Transmission operation enable
The TXDAn pin output is fixed to high level by setting the UAnTXE bit to 0.
Since the UAnTXE bit is initialized by the operating clock, to initialize the
transmission unit, set the UAnTXE bit from 0 to 1, and 2 clocks later, the
transmission enabled status is entered.
When the UAnPWR bit = 0, the value written to the UAnTXE bit is ignored.
Stop reception operation
Enable reception operation
UAnRXE
0
1
Reception operation enable
The receive operation is stopped by setting the UAnRXE bit to 0. Therefore,
even if the prescribed data is transferred, no reception completion interrupt is output
and the UAnRX register is not updated.
Since the UAnRXE bit is synchronized using the operating clock, to initialize the
reception unit, set the UAnRXE bit from 0 to 1, and 2 clocks later, the reception
enabled status is entered.
When the UAnPWR bit = 0, the value written to the UAnRXE bit is ignored.
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0