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CHAPTER 20 UART2, UART3
20.6
UART2, UART3 Baud Rates
One of the following can be selected for the UART2, UART3 serial clock source:
• Dedicated baud rate generator (Reload Counter)
• External clock as it is (clock input to the SCK2/SCK3 pin)
• External clock connected to the baud rate generator (Reload Counter)
■
UART2, UART3 Baud Rate Selection
Table 20.6-1 shows the select circuit of the baud rate. One of the following three types of baud rates can be
selected:
●
Baud rates determined using the dedicated baud rate generator (reload counter)
UART2, UART3 has two independent internal reload counters for transmission and reception serial clock.
The baud rate can be selected via the 15-bit reload value determined by the Baud Rate Generator Register 0
and 1 (BGR02/BGR03 and BGR12/BGR13).
The reload counter divides the machine clock by the value set in the Baud Rate Generator Register 0 and 1.
These baud rates are used in asynchronous mode or synchronous mode (master). To set the clock source,
select the internal clock and the use of the baud rate generator clock (SMR2/SMR3:EXT=0, OTO=0).
●
Baud rates determined using external clock (one-to-one mode)
The clock input from UART2, UART3 clock pulse input pins (SCK2/SCK3) is used as it is (synchronous).
Any baud rate less than the machine clock divided by 4 and is divisible can be set externally. These baud
rates are used in synchronous mode (slave). To set the clock source, select the external clock and its direct
use (SMR2/SMR3:EXT=1, OTO=1).
●
Baud rates determined using the dedicated baud rate generator with external clock
An external clock source can also be connected internally to the reload counter. In this mode it is used
instead of the internal machine clock. Baud rates can be selected by setting baud rate generator registers 1
and 0 (BGR02/BGR03, BGR12/BGR13) to 15-bit reload values. The reload counter divides the external
clock frequency by the set value. These baud rates are used in asynchronous mode. To set the clock source,
select the external clock and the use of the baud rate generator clock (SMR2/SMR3:EXT=1, OTO=0). This
was designed to use quartz oscillators with special frequencies and having the possibility to divide them.
Summary of Contents for MB90390 Series
Page 2: ......
Page 4: ......
Page 17: ...xiii APPENDIX D List of Interrupt Vectors 690 INDEX 695 ...
Page 18: ...xiv ...
Page 132: ...104 CHAPTER 5 CLOCKS ...
Page 152: ...124 CHAPTER 6 CLOCK MODULATOR ...
Page 210: ...182 CHAPTER 11 TIME BASE TIMER ...
Page 218: ...190 CHAPTER 12 WATCHDOG TIMER ...
Page 264: ...236 CHAPTER 14 16 BIT RELOAD TIMER WITH EVENT COUNT FUNCTION ...
Page 274: ...246 CHAPTER 15 WATCH TIMER ...
Page 306: ...278 CHAPTER 17 DTP EXTERNAL INTERRUPTS ...
Page 338: ...310 CHAPTER 18 8 10 BIT A D CONVERTER ...
Page 364: ...336 CHAPTER 19 UART0 UART1 ...
Page 398: ...370 CHAPTER 20 UART2 UART3 Figure 20 5 2 ORE Set Timing Receive data RDRF ORE ...
Page 432: ...404 CHAPTER 20 UART2 UART3 ...
Page 482: ...454 CHAPTER 22 SERIAL I O ...
Page 560: ...532 CHAPTER 24 STEPPING MOTOR CONTROLLER ...
Page 582: ...554 CHAPTER 27 ROM MIRRORING MODULE ...
Page 632: ...604 CHAPTER 29 EXAMPLES OF SERIAL PROGRAMMING CONNECTION ...
Page 722: ...694 APPENDIX ...
Page 723: ...695 INDEX The index follows on the next page This is listed in alphabetic order ...
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