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MB90335 Series
18.8
Notes on Using UART
Use of the UART requires the following cautions.
■ Notes on Using UART
●
Enabling sending and receiving
• The bits indicating that sending operation is enabled (SCR0, SCR1: TXE) and that receiving operation is
enabled (SCR0, SCR1: RXE) is provided for sending and receiving respectively.
• In the initial state after a reset, transmission and reception are both disabled (SCR0, SCR1:TXE=0,
RXE=0). Transmission and reception must therefore be enabled in advance.
• The device can stop transmission and reception by disabling them (SCR0, SCR1:TXE=0,RXE=0).
●
Setting operation mode
Set the operation mode after disabling transmission and reception (SCR0, SCR1:TXE=0,RXE=0). When
the operation mode is changed during transmission or reception, the transmitted/received data is not
guaranteed.
●
About clock synchronous mode
Operation mode 2 is set as a clock synchronizer method. Transmit/receive data is associated with no start
and stop bits.
●
Transmission interrupt enable timing
The sending data empty flag bit (SSR0, SSR1: TDRE) is set to "1" (no sending data, enabled to write
sending data) by default after resetting. So, as soon as a sending interrupt is enabled (SSR0, SSR1: TIE=1),
the sending interrupt request is generated. Be sure to prepare data to transmit before enabling transmission
(SSR0, SSR1:TIE=1).
●
Receiving Multiprocessor mode
In the multiprocessor mode, receiving operation based on 9-bit receipt is not allowed.
CM44-10137-6E
FUJITSU MICROELECTRONICS LIMITED
CHAPTER 18 UART
18.8 Notes on Using UART
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