CHAPTER 11 SERIAL INTERFACE UART0 (
µ
PD78F0102H AND 78F0103H ONLY)
Preliminary User’s Manual U16846EJ1V0UD
211
11.4 Operation of Serial Interface UART0
Serial interface UART0 has the following two modes.
•
Operation stop mode
•
Asynchronous serial interface (UART) mode
11.4.1 Operation stop mode
In this mode, serial communication cannot be executed, thus reducing the power consumption. In addition, the
pins can be used as ordinary port pins in this mode. To set the operation stop mode, clear bits 7, 6, and 5 (POWER0,
TXE0, and RXE0) of ASIM0 to 0.
(1) Register
used
The operation stop mode is set by asynchronous serial interface operation mode register 0 (ASIM0).
ASIM0 can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets this register to 01H.
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 1
Disables operation of the internal operation clock (fixes the clock to low level) and asynchronously
resets the internal circuit
Note 2
.
TXE0
Enables/disables
transmission
0
Disables
transmission
(synchronously resets the transmission circuit).
RXE0
Enables/disables
reception
0
Disables
reception
(synchronously resets the reception circuit).
Notes 1. The input from the R
X
D0 pin is fixed to high level when POWER0 = 0.
2. Asynchronous serial interface reception error status register 0 (ASIS0), transmit shift register 0 (TXS0),
and receive buffer register 0 (RXB0) are reset.
Caution Clear POWER0 to 0 after clearing TXE0 and RXE0 to 0 to set the operation stop mode.
To start the operation, set POWER0 to 1, and then set TXE0 and RXE0 to 1.
Remark To use the RxD0/SI10/P11 and TxD0/SCK10/P10 pins as general-purpose port pins, see CHAPTER 4
PORT FUNCTIONS.