User's Guide

ME910C1 HW User Guide
1VV0301351 Rev. 2 Page 48 of 81 2017-07-19
5.6.2.3. Modem serial port 2 (USIF1)
The secondary serial port on the ME910C1 is a CMOS1.8V with only the RX and TX
signals.
The signals of the ME910C1 serial port are:
PAD Signal I/O Function Type NOTE
D15 TX_AUX O
Auxiliary UART (TX Data to
DTE)
CMOS
1.8V
Shared
with
SPI_MOSI
E15 RX_AUX I
Auxiliary UART (RX Data from
DTE)
CMOS
1.8V
Shared
with
SPI_MISO
NOTE:
Due to the shared pins, when the Modem Serial port is
used, it is not possible to use the SPI functions.
In order to avoid a back powering effect it is recommended
to avoid having any HIGH logic level signal applied to the
digital pins of the ME910C1 when the module is powered
off or during an ON/OFF transition.
5.6.2.4. RS232 level translation
In order to interface the ME910C1 with a PC com port or a RS232 (EIA/TIA-232)
application a level translator is required. This level translator must:
• invert the electrical signal in both directions;
• Change the level from 0/1.8V to +15/-15V.
Actually, the RS232 UART 16450, 16550, 16650 & 16750 chipsets accept signals with
lower levels on the RS232 side (EIA/TIA-562), allowing a lower voltage-multiplying ratio