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14.3 Pins of the UART/SIO
14.3 Pins of the UART/SIO
This section shows the pins related to the UART/SIO and shows a block diagram of the
pins.
I
Pins Related to the UART/SIO
The pins related to UART/SIO include the clock I/O pin (P40/SCL3/UCK1), the serial data output
pin (P65/U01), and the serial data input pin (P41/SDA3/UI1). All of which can be switched by
the bridge circuit selection register (BRSR3) and the operating port selection bit (SMC2: SCKE).
P40/SCL3/UCK1 pin
The P40/SCL3/UCK1 pin serves as a general-purpose I/O port (P40), a clock I/O pin
(hysteresis input) of the UART/SIO (UCK1), and the clock line of the I
2
C bus (SCL3). When
clock output is permitted (SMC2: SCKE = 1), this pin serves as a clock I/O pin of the UART/
SIO (UCK1) irrespective of the value of the corresponding port direction register. At this
time, do not select the external clock (SMC1: CLK2. CLK1, CLK0 is other than 100
B
). When
this pin is used as a clock input pin of the UART/SIO, prohibit clock output (SMC: SCKE = 0)
and set it to Hiz with the corresponding port data register (PDR4: bit0 = 1). Also at this time,
select the external clock (SMC1: CLK2. CLK1, CLK0 = 100
B
).
P65/U01
The P65/U01 pin serves as a general-purpose I/O port (P65) and a serial data output pin of
the UART/SIO (U01). When serial data output is permitted (SMC2: TXOE = 1), this pin
serves as a serial data output pin of the UART/SIO (U01) irrespective of the value of the
corresponding port direction register.
P41/SDA3/UI1 pin
The P41/SDA3/UI1 pin serves as a general-purpose I/O port (P41), a serial data input pin
(hysteresis input) of the UART/SIO (UCK1), and the data line of the I
2
C bus (SDA3). When
this pin is used as a serial data input pin of the UART/SIO, set it to Hiz with the
corresponding port data register (PDR4: bit1 = 1).