R8C/18 Group, R8C/19 Group
15. Serial Interface
Rev.1.30
Apr 14, 2006
Page 159 of 233
REJ09B0222-0130
Figure 15.10
Transmit Timing in UART Mode
Transfer clock
D0
TE bit in UiC1
register
TXDi
Set to 0 when interrupt request is acknowledged, or set by a program
• Transmit timing when transfer data is 8 bits long (parity enabled, 1 stop bit)
Write data to UiTB register
TC
D1
D2
D3
D4
D5
D6
D7
P
SP
TC = 16 (n + 1) / fj or 16 (n + 1) / fEXT
fj: Frequency of UiBRG count source (f1, f8, f32)
fEXT: Frequency of UiBRG count source (external clock)
n: Value set in UiBRG register
I = 0 or 1
The above timing diagram applies under the following conditions:
• PRYE bit in UiMR register = 1 (parity enabled)
• STPS bit in UiMR register = 0 (1 stop bit)
• UiIRS bit in UCON register = 1 (an interrupt request is generated when transmit completes)
ST
D0
D1
D2
D3
D4
D5
D6
D7
P
SP
ST
D0
D1
ST
Start bit
Parity
bit
Stop pulsing
because the TE bit is set to 0
D0
TXDi
Write data to UiTB register
Transfer from UiTB register to UARTi transmit register
TC
D1
D2
D3
D4
D5
D6
D7
D8
SP SP
ST
D0
D1
D2
D3
D4
D5
D6
D7
D8
SP SP
ST
D0
D1
ST
TI bit in UiC1
register
1
0
1
0
1
0
1
0
TXEPT bit in
UiC0 register
IR bit in SiTIC
register
Stop
bit
• Transmit timing when transfer data is 9 bits long (parity disabled, 2 stop bits)
1
0
Stop
bit
Stop
bit
Start bit
Transfer clock
TE bit in UiC1
register
TI bit in UiC1
register
TXEPT bit in
UiC0 register
IR bit in SiRIC
register
1
0
1
0
1
0
Transfer from UiTB register to UARTi transmit register
TC = 16 (n + 1) / fj or 16 (n + 1) / fEXT
fj: Frequency of UiBRG count source (f1, f8, f32)
fEXT: Frequency of UiBRG count source (external clock)
n: Value set in UiBRG register
i = 0 or 1
Set to 0 when interrupt request is acknowledged, or set by a program
The above timing diagram applies under the following conditions:
• PRYE bit in UiMR register = 0 (parity disabled)
• STPS bit in UiMR register = 1 (2 stop bits)
• UiIRS bit in UCON register = 0 (an interrupt request is generated when transmit buffer is empty)