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13 UART (UART2)
13.2 Input/Output Pins and External Connections
13.2.1 List of Input/Output Pins
Table 13.2.1.1 lists the UART2 pins.
Pin name
USINn
USOUTn
If the port is shared with the UART2 pin and other functions, the UART2 input/output function must be assigned to
the port before activating the UART2. For more information, refer to the "I/O Ports" chapter.
13.2.2 External Connections
Figure 13.2.2.1 shows a connection diagram between the UART2 in this IC and an external UART device.
Figure 13.2.2.1 Connections between UART2 and an External UART Device
13.2.3 Input Pin Pull-Up Function
The UART2 includes a pull-up resistor for the USINn pin. Setting the UART2_nMOD.PUEN bit to 1 enables the
resistor to pull up the USINn pin.
13.2.4 Output Pin Open-Drain Output Function
The USOUTn pin supports the open-drain output function. Default configuration is a push-pull output and it is
switched to an open-drain output by setting the UART2_nMOD.OUTMD bit to 1.
13.2.5 Input/Output Signal Inverting Function
The UART2 can invert the signal polarities of the USINn pin input and the USOUTn pin output by setting the
UART2_nMOD.INVRX bit and the UART2_nMOD.INVTX bit, respectively, to 1.
Note: Unless otherwise specified, this chapter shows input/output signals with non-inverted wave-
forms (UART2_nMOD.INVRX bit = 0, UART2_nMOD.INVTX bit =0).
13.3 Clock Settings
13.3.1 UART2 Operating Clock
When using the UART2 Ch.n, the UART2 Ch.n operating clock CLK_UART2_n must be supplied to the UART2
Ch.n from the clock generator. The CLK_UART2_n supply should be controlled as in the procedure shown below.
1. Enable the clock source in the clock generator if it is stopped (refer to "Clock Generator" in the "Power Supply,
Reset, and Clocks" chapter).
2. Set the following UART2_nCLK register bits:
- UART2_nCLK.CLKSRC[1:0] bits
- UART2_nCLK.CLKDIV[1:0] bits
The UART2 operating clock should be selected so that the baud rate generator will be configured easily.
13-2
Table 13.2.1.1 List of UART2 Pins
I/O*
Initial status*
I
I (Hi-Z)
O
O (High)
* Indicates the status when the pin is configured for the UART2.
USINn
USOUTn
S1C31 UART2
(Clock source selection)
(Clock division ratio selection = Clock frequency setting)
Seiko Epson Corporation
Function
UART2 Ch.n data input pin
UART2 Ch.n data output pin
OUT
IN
External UART
S1C31W74 TECHNICAL MANUAL
(Rev. 1.1)
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