Preliminary User’s Manual U16846EJ1V0UD
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CHAPTER 11 SERIAL INTERFACE UART0 (
µ
PD78F0102H AND 78F0103H ONLY)
11.1 Functions of Serial Interface UART0
Serial interface UART0 has the following two modes.
(1) Operation stop mode
This mode is used when serial communication is not executed and can enable a reduction in the power
consumption.
For details, see 11.4.1 Operation stop mode.
(2) Asynchronous serial interface (UART) mode
The functions of this mode are outlined below.
For details, see 11.4.2 Asynchronous serial interface (UART) mode and 11.4.3 Dedicated baud rate
generator.
•
Two-pin
configuration T
X
D0: Transmit data output pin
R
X
D0: Receive data input pin
•
Length of communication 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 communication
Cautions 1. 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
X
D0 pin also holds the value immediately before clock supply was
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.
2. Set POWER0 = 1 and then set TXE0 = 1 (transmission) or RXE0 = 1 (reception) to start
communication.
3. TXE0 and RXE0 are synchronized by the base clock (f
XCLK0
) set by BRGC0. To enable
transmission or reception again, set TXE0 or RXE0 to 1 at least two clocks of base clock
after TXE0 or RXE0 has been cleared to 0. If TXE0 or RXE0 is set within two clocks of base
clock, the transmission circuit or reception circuit may not be initialized.
