Input/Output Pins And External Connections; List Of Input/Output Pins; External Connections; Input Pin Pull-Up Function - Epson S1C17M20 Technical Manual

12 UART (UART3)

12.2 Input/Output Pins and External Connections

12.2.1 List of Input/Output Pins

Table 12.2.1.1 lists the UART3 pins.
Pin name
USINn
USOUTn
If the port is shared with the UART3 pin and other functions, the UART3 input/output function must be assigned to
the port before activating the UART3. For more information, refer to the "I/O Ports" chapter.

12.2.2 External Connections

Figure 12.2.2.1 shows a connection diagram between the UART3 in this IC and an external UART device.
Figure 12.2.2.1 Connections between UART3 and an External UART Device

12.2.3 Input Pin Pull-Up Function

The UART3 includes a pull-up resistor for the USINn pin. Setting the UAnMOD.PUEN bit to 1 enables the resistor
to pull up the USINn pin.

12.2.4 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 UAnMOD.OUTMD bit to 1.

12.2.5 Input/Output Signal Inverting Function

The UART3 can invert the signal polarities of the USINn pin input and the USOUTn pin output by setting the UAn-
MOD.INVRX bit and the UAnMOD.INVTX bit, respectively, to 1.
Note: Unless otherwise specified, this chapter shows input/output signals with non-inverted wave-
forms (UAnMOD.INVRX bit = 0, UAnMOD.INVTX bit =0).

12.3 Clock Settings

12.3.1 UART3 Operating Clock

When using the UART3 Ch.n, the UART3 Ch.n operating clock CLK_UART3_n must be supplied to the UART3
Ch.n from the clock generator. The CLK_UART3_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 UAnCLK register bits:
- UAnCLK.CLKSRC[1:0] bits (Clock source selection)
- UAnCLK.CLKDIV[1:0] bits (Clock division ratio selection = Clock frequency setting)
The UART3 operating clock should be selected so that the baud rate generator will be configured easily.
12-2
Table 12.2.1.1 List of UART3 Pins
I/O* Initial status*
I I (Hi-Z)
O O (High)
* Indicates the status when the pin is configured for the UART3.
USINn
USOUTn
S1C17 UART3
Seiko Epson Corporation
Function
UART3 Ch.n data input pin
UART3 Ch.n data output pin
OUT
IN
External UART
S1C17M20/M21/M22/M23/M24/M25
TECHNICAL MANUAL (Rev. 1.0)