Precautions On Use Of The Uart - Fujitsu MB90480 Series Hardware Manual

19.6 Precautions on use of the UART

Notes the following points when using the UART.
■
Precautions on use of the UART
❍ Enabling operation
The serial control register (SCR) of the UART contains operation enable bits for enabling
sending and receiving, namely, TXE (sending) and RXE (reception).
By default (initial value), both sending and receiving are disabled. If required, enable the
operation.
❍ Communication mode setting
Set the communication mode while the UART is not in operation. Transmission and reception
data cannot be assured if the mode is changed during data transmission or reception.
❍ Synchronous mode
The clock synchronous mode (operation mode 2) of the UART uses a clock control (expanded I/O
serial) operation, and a start bit or stop bit is not added to data.
❍ Transmission data empty flag bit
By default (initial value), the transmission data empty flag bit (TDRE of SSR) is set to "1" (no
transmission data, transmission data can be written). Therefore, when transmission interrupt
requests are enabled (TIE = 1 of SSR), a transmission interrupt request will be triggered
immediately. Be sure that the sending data is available before setting the TIE flag to "1".
❍ Clock setting in synchronous transfer
• Please do not use the following settings when the dedicated baud rate generator is used at
the synchronous transmission.
1) CS2 to CS0 = 000
2) CS2 to CS0 = 001
• Please do not use the following settings when the internal timer (PPG1) is used at the
synchronous transmission.
N = 1, n = 0
B
, DIV3 to DIV0 = 0000
B B
CHAPTER 19 UART
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