I'm curious: what is the purpose of the UART scratch register? Does it exist for historical purposes?
Scratch register (UART_SCR) is used for general-purpose data storage and does not control the UART hardware in any way. It can be used for storing some UART related information while dealing with UART in the application otherwise it does not control the UART in any way. If you want to know more about the history of UART controller you can visit : http://www.lammertbies.nl/comm/info/serial-uart.html#SCR.
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