CHAPTER 13 SERIAL INTERFACE UART0
Preliminary User’s Manual U16315EJ1V0UD
249
13.3 Registers Controlling Serial Interface UART0
Serial interface UART0 is controlled by the following three registers.
•
Asynchronous serial interface operation mode register 0 (ASIM0)
•
Asynchronous serial interface reception error status register 0 (ASIS0)
•
Baud rate generator control register 0 (BRGC0)
(1) Asynchronous serial interface operation mode register 0 (ASIM0)
This 8-bit register controls the serial transfer operations of serial interface UART0.
This register can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets this register to 01H.
Figure 13-2. Format of Asynchronous Serial Interface Operation Mode Register 0 (ASIM0) (1/2)
Address: FF70H After reset: 01H R/W
Symbol
7
6
5
4
3
2
1
0
ASIM0
POWER0
TXE0
RXE0
PS01
PS00
CL0
SL0
1
POWER0
Enables/disables operation of internal operation clock
0
Note
Disables operation of the internal operation clock (fixes the clock to low level) and asynchronously
resets the internal circuit.
1
Enables operation of the internal operation clock.
TXE0
Enables/disables transmission
0
Disables transmission (synchronously resets the transmission circuit).
1
Enables transmission.
RXE0
Enables/disables reception
0
Disables reception (synchronously resets the reception circuit).
1
Enables reception.
Note
The input from the R
X
D0 pin is fixed to high level when POWER0 = 0.
Cautions 1. At startup, set POWER0 to 1 and then set TXE0 to 1. Clear TXE0 to 0 first, and then clear
POWER0 to 0.
2. At startup, set POWER0 to 1 and then set RXE0 to 1. Clear RXE0 to 0 first, and then clear
POWER0 to 0.
3. TXE0 and RXE0 are synchronized with the base clock (f
XCLK
) set by BRGC0. Therefore, the
transmission unit may not be initialized if TXE0 = 1 is not set again 2 clocks after TXE0 = 0 is
set. Similarly, the reception unit may not be initialized if RXE0 = 1 is not set again 2 clocks
after RXE0 = 0 is set.
4. Be sure to set bit 0 to 1.