CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U14492EJ3V0UD
418
10.2.3 Control registers
(1) Asynchronous serial interface mode register 0 (ASIM0)
The ASIM0 register is an 8-bit register that controls the UART0 transfer operation.
This register can be read/written in 8-bit or 1-bit units.
Caution
When using UART0, be sure to set the external pins related to the UART0 function to the
control mode before setting clock selection register 0 (CKSR0) and baud rate generator
control register 0 (BRGC0), and then set the UARTCAE0 bit to 1. Then set the other bits.
(1/3)
<7>
UARTCAE0
ASIM0
<6>
TXE0
<5>
RXE0
4
PS1
3
PS0
2
CL
1
SL
0
ISRM
Address
FFFFFA00H
Initial value
01H
Bit Position
Bit Name
Function
7
UARTCAE0
Controls the operating clock.
0: Stops clock supply to UART0.
1: Supplies clock to UART0.
Cautions 1. When UARTCAE0 = 0 is set, UART0 is asynchronously reset.
2. When UARTCAE0 = 0, UART0 is in a reset state. To operate
UART0, first set UARTCAE0 = 1.
3. When the UARTCAE0 bit is changed from 1 to 0, all the registers
of UART0 are initialized. When setting UARTCAE0 = 1 again, be
sure to re-set the registers of UART0.
The output of the TXD0 pin goes high when transmission is disabled, regardless of
the setting of the UARTCAE0 bit.
6
TXE0
Enables/disables transmission.
0: Disable transmission
1: Enable transmission
Cautions 1. Set the TXE0 bit to 1 after setting the UARTCAE0 bit to 1 at
startup. Set the UARTCAE0 bit to 0 after setting the TXE0 bit to
0 to stop.
2. To initialize the transmission unit, clear (0) the TXE0 bit, and
after letting 2 cycles of the base clock elapse, set (1) the TXE0
bit again. If the TXE0 bit is not set again, initialization may not
be successful (for details about the base clock, refer to 10.2.6
(1) (a) Base clock).
Содержание V850E/IA1 mPD703116
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