Precautions On Using The Uart - Fujitsu F2MC-16LX Hardware Manual

CHAPTER 21 UART

21.4 Precautions on Using the UART

This section lists caution remarks applying to the use of the UART.
I Precautions on using the UART
❍ Enabling operation
The control register (SCR) of the UART contains operation enable bits for enabling sending and
receiving, namely, TXT (sending) and RXE (reception).
By default (as initial value), both sending and receiving must be disabled to stop data transfer. If
required, data transfer can also be disabled during operation.
❍ Communication Mode Setting
Set the communication mode while the converter 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 (as 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 send data is available before setting the TIE flag to "1".
❍ Clock division ratio of 1/1 in synchronous transfer
The use of a cock division ratio 1/1 (CS2 to CS0 = 000
420
) in synchronous transfer is prohibited.
B