EMX-ESG User Manual Rev A.1
www.diamondsystems.com
Page 6
3.3 Serial Ports
EMX-ESG includes an SMSC SCH3116 6-port UART to provide 6 serial ports. Ports 1-4 use Exar SP336
multiprotocol transceivers to support RS-232, RS422, and RS-485. On these ports, signals TX, RX, CTS, and
RTS are available in RS-232 mode. In RS-485 mode, the transmitter is controlled by the RTS line.
Ports 5-6 have only TX and RX signals. These ports offer RS-232 or logic level I/O. These ports can optionally be
used to communicate with an installed GPS receiver. To do so, both the RS-232 and logic level transceivers are
disabled.
Serial ports 1-2 share one SP336 for protocol selection, and ports 3-4 share a second SP336. Each SP336
requires 2 jumpers for protocol selection, connected to mode pins M0 and M2. Mode pin M1 is tied high for all
protocols.
Ports 1-4 each require 3 jumpers for termination and bias resistors when configured for RS-422 or RS-485 mode.
The termination resistor value is 121 ohms 1%, and the bias resistors are 4.75K ohms 1%.
Ports 5-6 use an SP3245 for RS-232 mode or a logic level driver for logic level signals. Configuration is done as
an assembly option
– both transceivers cannot be simultaneously installed for the same port. Each port can be
configured separately. Two jumpers are required for each port to provide independent enable / disable signals for
each driver/transceiver chip in case a GPS module is installed.
All protocol selection and termination / bias resistor selections are made with jumpers. The board contains 0-ohm
resistors that may be installed in place of all jumpers for a more rugged assembly.
3.4 General Purpose I/O
The EMX-ESG offers 14 general purpose digital I/O lines which are provided on an I/O connector. These lines
offer 3.3V logic levels with 5V compatibility. The ports have programmable direction with I/O buffers for protection.
The buffer direction control signals are derived from three other GPIO lines on the SCH3116. On power-up, the
digital I/O ports are in input mode. The digital I/O lines have jumper-configured pull-up/down resistors.
3.5 GPS
EMX-ESG supports a Condor C2626 23-channel GPS receiver.
