VR4102 datasheet(67/701 Pages) NEC

67 / 701 page

CHAPTER 2 PIN FUNCTIONS

2.2.5 RS-232-C Interface Signals

These signals control data transmission and reception between the VR4102 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

This is a receive data signal. It is used when the RS-232-C controller sends serial data to the VR4102.

CTS#

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]

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 VR4102.

When this pin is not used for DCD# signal, this pin can be used as an interrupt detection function for the

GIU unit.

DSR#

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 VR4102.

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 VR4102 sends serial data to the RS-232C controller.

RTS# signal (output):

This is a transmit request signal. This signal is asserted when the VR4102 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 VR4102 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

RFU

110

RFU

101

53.6 MHz

6.700 MHz

100

49.2 MHz

6.075 MHz

011

45.4 MHz

5.675 MHz

010

42.1 MHz

5.275 MHz

001

36.9 MHz

9.200 MHz

000

32.8 MHz

8.200 MHz

Caution Some of these settings of frequency may not be able to select in the future.

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