User's Manual

LE920A4 HW User Guide Hardware Interfaces

Doc#: 1VV0301261

Rev. 4.3 Page 72 of 123 2017-12-07

NOTE:

ETH_INT_N is a 1.8V input. It has an internall pull up to 1.8V inside the

module thus it should be connected to an open drain interrupt pin of the

Ethernet PHY. In case the PHY does not support 1.8V I/O, proper level

shifter needs to be used.

Serial Ports

The serial port is typically a secondary interface between the module and OEM hardware.

Two serial ports are available on the module:

• MODEM SERIAL PORT 1(Main)

• MODEM SERIAL PORT 2 (Auxiliary)

Several configurations can be designed for the serial port on the OEM hardware. The

most common are:

• RS232 PC com port

• Microcontroller UART @ 1.8V (Universal Asynchronous Receive Transmit)

• Microcontroller UART @ 3.3V/5V or other voltages different from 1.8V

Depending on the type of serial port on the OEM hardware, a level translator circuit may

be needed to make the system operate. The only configuration that does not need level

translation is the 1.8V UART.

The levels for the module’s UART are the CMOS levels as described in Section 4.3, Logic

Level Specifications.

8.4.1. Modem Serial Port 1

Serial Port 1 is a +1.8V UART with all 8 RS232 signals.

It differs from the PC-RS232 in the signal polarity (RS232 is reversed) and levels.

Table 27 Serial Port 1 Signals

RS232

Number

Signal

Pad

Number

Name Usage

DCD -

DCD_UART

AE18

Data Carrier

Detect

Output from the module that

indicates carrier presence

RXD -

TX_UART

AF19

Transmit line

*see Note

Output transmit line of the module

UART