CHAPTER 2 PIN FUNCTIONS
User’s Manual U14272EJ3V0UM
57
2.2.9 Serial interface channel 1 signals
Signal name
I/O
Description of function
RxD1/GPIO25
I/O
Serial channel 1 receive data input or general-purpose I/O.
TxD1/GPIO26/CLKSEL0
I/O
The function of this pin differs depending on the operating status.
<During RTC reset (input)>
This signal is used to set CPU core operation clock frequency
Note
.
<During normal operation (input/output)>
Serial channel 1 transmit data output or general-purpose I/O.
RTS1#/GPIO27/CLKSEL1
I/O
The function of this pin differs depending on the operating status.
<During RTC reset (input)>
This signal is used to set CPU core operation clock frequency
Note
.
<During normal operation (input/output)>
Serial channel 1 request to send output or general-purpose I/O.
CTS1#/GPIO28
I/O
Serial channel 1 clear to send input or general-purpose I/O.
DCD1#/GPIO29
I/O
Serial channel 1 data carrier detect input or general-purpose I/O.
DTR1#/GPIO30/CLKSEL2
I/O
The function of this pin differs depending on the operating status.
<During RTC reset (input)>
This signal is used to set CPU core operation clock frequency
Note
.
<During normal operation (input/output)>
Serial channel 1 data terminal ready output or general-purpose I/O.
DSR1#/GPIO31
I/O
Serial channel 1 Data set ready input or general-purpose I/O.
Note CLKSEL(2:0) signals are used to set the frequency of the CPU core operation clock (PClock). These signals
are sampled when the RTCRST# signal goes high.
The relationship between the CLKSEL(2:0) pin settings and clock frequency is shown below.
CLKSEL(2:0)
CPU core operation frequency (PClock)
111
Reserved (98.1 MHz)
110
Reserved (90.6 MHz)
101
Reserved (84.1 MHz)
100
Reserved (78.5 MHz)
011
Reserved (69.3 MHz)
010
65.4 MHz
001
62.0 MHz
000
49.1 MHz
TClock is generated from PClock and its frequency is always 1/2 of the PClock frequency after RTC reset.