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11 UART (UART)
11.2 Input/Output Pins and External Connections
11.2.1 List of Input/Output Pins
Table 11.2.1.1 lists the UART pins.
Pin name
USINn
USOUTn
If the port is shared with the UART pin and other functions, the UART input/output function must be assigned to
the port before activating the UART. For more information, refer to the "I/O Ports" chapter.
11.2.2 External Connections
Figure 11.2.2.1 shows a connection diagram between the UART in this IC and an external UART device.
Figure 11.2.2.1 Connections between UART and an External UART Device
11.2.3 Input Pin Pull-Up Function
The UART 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.
11.2.4 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.
11.3 Clock Settings
11.3.1 UART Operating Clock
When using the UART Ch.n, the UART Ch.n operating clock CLK_UARTn must be supplied to the UART Ch.n
from the clock generator. The CLK_UARTn 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 UART operating clock should be selected so that the baud rate generator will be configured easily.
11.3.2 Clock Supply in SLEEP Mode
When using the UART during SLEEP mode, the UART operating clock CLK_UARTn must be configured so that
it will keep supplying by writing 0 to the CLGOSC.xxxxSLPC bit for the CLK_UARTn clock source.
11-2
Table 11.2.1.1 List of UART Pins
I/O*
Initial status*
I
I (Hi-Z)
O
O (High)
USINn
USOUTn
S1C17 UART
Seiko Epson Corporation
UART Ch.n data input pin
UART Ch.n data output pin
* Indicates the status when the pin is configured for the UART.
OUT
IN
External UART
Function
S1C17M01 TECHNICAL MANUAL
(Rev. 1.2)
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