
16.1.2.4 TXD and RXD I/O Polarity Inverse
As shown in
Figure 16.19, the level output from the TXD pin and the level applied to the RXD pin are inverted
with this function. All I/O data levels, including the start bit, stop bit and parity bit, are inverted.
Figure 16.19
TXD and RXD I/O Polarity Inverse
16.1.2.5 CTS/RTS Function
When the CTS function is used, the transmit/receive operation starts when a low-level (“L”) signal is applied to
the CTSi pin (i = 0 to 4). When a high-level (“H”) signal is applied to the CTSi pin during transmitting/
receiving, the transmit/receive operation stops after the ongoing transmit/receive operation is completed. To use
the CTS function, select the I/O port with the function select register, set the CRD bit in the UiC0 register to 0
(CTS function enabled), and set the CRS bit in the UiC0 register to 0 (CTS function selected).
When the RTS function is used, the RTSi pin outputs an “H” at the first falling edge of the clock input to the
CLKi pin, and outputs an “L” under the following conditions.
The RI bit in the UiC1 register is 0 (no data in the UiRB register).
The TE bit in the UiC1 register is set to 1 (transmit operation enabled).
The RE bit in the UiC1 register is set to 1 (receive operation enabled).
The TI bit in the UiC1 register is 0 (data in the UiTB register).
To use the RTS function, select the RTSi pin with the function select register.
(1) When the IOPOL bit in the UiMR register (i = 0 to 4) is set to 0 (not inverted)
(2) When the IOPOL bit is set to 1 (inverted)
TXDi
(not inverted)
NOTE:
1. The above applies when the UFORM bit in the UiC0 register is set to 0 (LSB first), the STPS bit in the UiMR
register is set to 0 (1 stop bit), and the PRYE bit is set to 1 (parity enabled).
ST: Start bit
P: Parity bit
SP: Stop bit
"H"
"L"
ST
D0
D2
D3
D4
D5
SP
D1
D6
D7
P
ST
D0
D2
D3
D4
D5
SP
D1
D6
D7
P
RXDi
(not inverted)
"H"
"L"
ST
D0
D2
D3
D4
D5
SP
D1
D6
D7
P
ST
D0
D2
D3
D4
D5
SP
D1
D6
D7
P
TXDi
(inverted)
"H"
"L"
RXDi
(inverted)
"H"
"L"