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CHAPTER 10 UART
10.2 Structure of UART
The UART consists of the following blocks:
• Baud rate generator and serial clock generator
• Data transmitter and data receiver
• Registers (SMC1, SMC2, SRC, SSD, SIDR, SODR)
■ Block diagram of UART
Figure 10.2-1 Block diagram of UART
P45/SCK
CPU clock
1/4
1/6
1/13
1/65
PDS1
PDS0
PWM timer
output
1/2
n
1/4
1/2
1/8
RC2
RC1
RC0
CS1
CS0
CR
SMDE
UART serial clock
RSEL
SCKE*
1
Serial I/O clock
P45/SCK
1/2
Serial
clock
Baud rate generator and serial clock generator
Data transmit control circuit
Data receive control circuit
P43/SI
Start bit
detection
Start
Reset
Receiver
byte count
Shift clock
Transfer clock
Shifter
SIDR
Parity
generator
CR
RDRF
ORFE
Transmitter
byte count
Timing
Reset
Transmitter
control
Shift clock
Transfer clock
Shifter
SODR
Parity
generatorTDRE
RD8/RP
RSEL
SOE*
2
P44/SO
Serial I/O data
PEN
MC1
MC0
PEN
TD8/TP
MC1
MC0
SBL
ORFE
RDRF
RIE
TDRE
TIE
Internal data bus
Registers:
SMC1 PEN SBL MC1 MC0
SMDE —
SCKE SOE
SMC2
——
PSEN
—
RSEL
—
PDS1 PDS0
SSD RDRF ORFE TDRE TIE RIE
—
TD8/TP
RD8/RP
SRC
——
CR CS1 CS0 RC2 RC1 RC0
SODR
SIDR
IRQ4
*1: At switching between port output and serial clock output, the SCKE bit of the UART is valid when the RSEL bit is 0; the SCKE bit of the serial I/O is
valid when the RSEL bit is 1.
*2: At switching between port output and serial data output, the SOE bit of the UART is valid when the RSEL bit is 0; the SOE bit of the serial I/O is
valid when the RSEL bit is 1.