Notes On Using Uart - Fujitsu MB91150 Series Hardware Manual

15.10 Notes on Using UART

This section provides notes on using the UART.
I Notes on using the UART
❍ Operation enabled
The UART has the TXE (sending) and RXE (receiving) operation enable bits in the control
register (SCR0-3) separately for sending and receiving. Since both sending and receiving are
disabled in the default state (initial value), these operations must be enabled before performing
the transfer. The operations can be disabled to stop transfer as necessary.
❍ Communication mode setting
Set the communication mode while the UART is stopped. If the mode is set during a sending or
receiving operation, the integrity of the sent or received data cannot be guaranteed.
❍ Synchronization mode
The UART clock synchronization mode (operation mode 2) employs the clock control (I/O
extend serial) method and does not append the start bit and stop bit to data.
❍ Timing of enabling send interrupts
A send-interrupt request occurs immediately after the send-interrupt request is enabled (SSR0-
3: TIE = 1) because the default (initial value) of the send data empty flag bit (SSR0-3: TDRE) is
1 (no send data, send-data write enabled). The send data must be ready before the TIE flag is
set to 1.
CHAPTER 15 UART
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