Fujitsu FR81S User Manual
CHAPTER 40: MULTI-FUNCTION SERIAL INTERFACE
5. Operation of UART
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : MULTI-FUNCTION SERIAL INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
171
External Clock
When the EXT bit of the baud rate generator register (BGR) is set to "1", the baud rate generator divides the
external clock.
Note:
The external clock signals are synchronized with the internal clock by UART. If the external clock cannot
be synchronized, therefore, the operation becomes unstable.
Reload Counter Functions
Reload counters, including transmission and reception reload counters, serve as the dedicated baud rate
generators. It consists of a 15-bit register for reload values and generates a transmission/reception clock
from the external or internal clock.
Count Start
When a reload value is written to the baud rate generator register (BGR), the reload counter starts counting.
Restart
The reload counter restarts under one of the following conditions:
⋅
Common to the transmission and reception reload counters
⋅
Programmable reset (SCR:UPCL bit)
⋅
Reception reload counter
⋅
Detection of a start bit falling edge in asynchronous mode
MB91520 Series
MN705-00010-1v0-E
1484