Chapter 13 Serial Interface Uart0; Functions Of Serial Interface Uart0 - NEC 78K0/KD1 Series User Manual

13.1 Functions of Serial Interface UART0

Serial interface UART0 has the following two modes.
(1) Operation stop mode
This mode is used when serial transfer is not executed and can enable a reduction in the power consumption.
For details, refer to 13.4.1 Operation stop mode.
(2) Asynchronous serial interface (UART) mode
The functions of this mode are outlined below.
• Two-pin configuration
• Length of transfer data can be selected from 7 or 8 bits.
• Dedicated on-chip 5-bit baud rate generator allowing any baud rate to be set
• Transmission and reception can be performed independently.
• Four operating clock inputs selectable
• Fixed to LSB-first transfer
Cautions 1. The initial value of the T
port pin.
2. If clock supply to serial interface UART0 is not stopped (e.g., in the HALT mode), normal
operation continues. If clock supply to serial interface UART0 is stopped (e.g., in the STOP
mode), each register stops operating, and holds the value immediately before clock supply
was stopped. The T
stopped and outputs it. However, the operation is not guaranteed after clock supply is
resumed. Therefore, reset the circuit so that POWER0 = 0, RXE0 = 0, and TXE0 = 0.
3. Set POWER0 = 1 and then set TXE0 = 1 (transmission) or RXE0 = 1 (reception) to start
communication.
4. TXE0 and RXE0 are synchronized with the base clock (f
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.

CHAPTER 13 SERIAL INTERFACE UART0

T D0: Transmit data output pin
X
R B0: Receive data input pin
X
D0 pin is high level. Exercise care when using the T
X
D0 pin also holds the value immediately before clock supply was
X
Preliminary User's Manual U16315EJ1V0UD
D0 pin as a
X
) set by BRGC0. Therefore, the
XCLK
245