User's Guide

LE910Cx HW User Guide
Doc#: 1VV0301298
Rev. 13.0 Page 70 of 124 2019-07-15
Serial Ports
The serial port is typically a secondary interface between the LE910Cx module and OEM
hardware. The following serial ports are available on the module:
• Modem Serial Port 1 (Main)
• Modem Serial Port 2 (Auxiliary)
Several serial port configurations can be designed for 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 OEM hardware, level translator circuits may be
needed to make the system operate. The only configuration that does not need level
translation is the 1.8V UART.
The LE910Cx UART has CMOS levels as described in Section 4.3, Logic Level
Specifications.
8.4.1. Modem Serial Port 1 Signals
On the LE910Cx, Serial Port 1 is a +1.8V UART with 7 RS232 signals. It differs from the
PC-RS232 in the signal polarity (RS232 is reversed) and levels. Table 26 lists the signals
of LE910Cx Serial Port 1.
Table 26: Modem Serial Port 1 Signals
RS232
Pin#
Signal
Pad No.
Name
Usage
1
DCD -
DCD_UART
N14
Data Carrier
Detect
Output from LE910Cx that
indicates carrier presence
2
RXD -
TX_UART
M15
Transmit line
*see Note
Output transmit line of LE910Cx
UART
3
TXD -
RX_UART
N15
Receive line
*see Note
Input receive line of LE910Cx
UART
4
DTR -
DTR_UART
M14
Data
Terminal
Ready
Input to LE910Cx that controls
the DTE READY condition
5
GND
A2, B13,
D4…
Ground
Ground
6
DSR -
DSR_UART
P14
Data Set
Ready
Output from LE910Cx that
indicates that the module is
ready