
R8C/3GM Group
22. Serial Interface (UART2)
R01UH0284EJ0100 Rev.1.00
Aug 09, 2011
Figure 22.7
Transmit Timing in UART Mode
D0
D1
D2
D3
D4
D5
D6
D7
ST
P
Parity
bit
TXD2
CTS2
The above applies when:
PRYE bit in U2MR register = 1 (parity enabled)
STPS bit in U2MR register = 0 (one stop bit)
CRD bit in U2C0 register = 0 (CTS/RTS function enabled), CRS bit = 0 (CTS function selected)
U2IRS bit in U2C1 register = 1 (interrupt request generation when transmission is completed)
TC = 16(n + 1)/fj or 16(n + 1)/fEXT
fj: Frequency of U2BRG count source (f1, f8, f32, fC)
fEXT: Frequency of U2BRG count source (external clock)
n: Setting value in U2BRG
Set to 0 when an interrupt request is acknowledged or by a program.
D0
D1
D2
D3
D4
D5
D6
D7
ST
P
D0
D1
ST
TXD2
The above applies when:
PRYE bit in U2MR register = 0 (parity disabled)
STPS bit in U2MR register = 1 (two stop bits)
CRD bit in U2C0 register = 1 (CTS/RTS function disabled)
U2IRS bit in U2C1 register = 0 (interrupt request generation when the transmit buffer is empty)
Transfer clock
TC
Set to 0 when an interrupt request is acknowledged or by a program.
TC
Transfer clock
Stop
bit
Data is set in U2TB register.
Start bit
D0
D1
D2
D3
D4
D5
D6
D7
ST
D8
D0
D1
D2
D3
D4
D5
D6
D7
ST
D8
D0
D1
ST
SP SP
Stop
bit
The transfer clock stops once because “H” is applied to CTS pin when the stop bit is verified.
The transfer clock resumes running immediately after “L” is applied to CTS pin.
Data is set in U2TB register.
SP
Data transfer from U2TB register
to UART2 transmit register
Stop
bit
TE bit in
U2C1 register
TI bit in
U2C1 register
TXEPT bit in
U2C0 register
IR bit in
S2TIC register
TE bit in
U2C1 register
TI bit in
U2C1 register
TXEPT bit in
U2C0 register
IR bit in
S2TIC register
Pulsing stops because TE bit is set to 0.
SP
Start bit
SP
TC = 16(n + 1)/fj or 16(n + 1)/fEXT
fj: Frequency of U2BRG count source (f1, f8, f32, fC)
fEXT: Frequency of U2BRG count source (external clock)
n: Setting value in U2BRG
(1) Transmit Timing Example When Transfer Data is 8 Bits Long (Parity Enabled, One Stop Bit)
(2) Transmit Timing Example When Transfer Data is 9 Bits Long (Parity Disabled, Two Stop Bits)
Data transfer from U2TB register
to UART2 transmit register