CHAPTER 2 PIN FUNCTIONS
67
2.2.5 RS-232-C Interface Signals
These signals control data transmission and reception between the V
R
4102 and an RS-232-C controller. Table 2-
5 describes the functions of these signals.
Table 2-5. RS-232-C Interface Signals
Signal
I/O
Description of function
RxD
I
This is a receive data signal. It is used when the RS-232-C controller sends serial data to the V
R
4102.
CTS#
I
This is the transmit enable (“clear-to-send”) signal. This signal is asserted when the RS-232-C controller
is ready to receive transmission of serial data.
DCD#/
GPIO[15]
I
This is a carrier detection signal. This signal is asserted when valid serial data is being received. It is
also used when detecting a power-on factor for the V
R
4102.
When this pin is not used for DCD# signal, this pin can be used as an interrupt detection function for the
GIU unit.
DSR#
I
This is the data set ready signal. Assert this signal to set up transmission and reception of serial data
between the RS-232C controller and the V
R
4102.
TxD/
CLKSEL[2],
RTS#/
CLKSEL[1],
DTR#/
CLKSEL[0]
I/O
This function differs depending on the operating status.
In normal operation (output)
TxD signal (output):
This is a transmit data signal. It is used when the V
R
4102 sends serial data to the RS-232C controller.
RTS# signal (output):
This is a transmit request signal. This signal is asserted when the V
R
4102 is ready to receive serial
data from the RS-232C controller.
DTR# signal (output):
This is a terminal equipment ready signal. This signal is asserted when the V
R
4102 is ready to
transmit or receive serial data.
After RTC reset (input)
These signals are used to set the CPU core operation and BUSCLK frequency (CLKSEL[2..0]: input).
Sampling occurs when the RTCRST signal changes from low to high.
CLKSEL[2..0]
CPU Core frequency
BUSCLK frequency
111
110
101
100
011
010
001
000
RFU
RFU
53.6 MHz
49.2 MHz
45.4 MHz
42.1 MHz
36.9 MHz
32.8 MHz
RFU
RFU
6.700 MHz
6.075 MHz
5.675 MHz
5.275 MHz
9.200 MHz
8.200 MHz
Caution Some of these settings of frequency may not be able to select in the future.