2: Functional Description
xPico® 110 Wired Device Server Integration Guide
15
Serial Interface
The xPico 110 has two external serial interfaces. The signal levels on the serial interface are
3.3V logic level with 5V tolerant inputs. The serial interfaces require an external transceiver in
order to connect to external RS232, RS485, or RS422 networks. The signals of Serial Port 1 may
be connected as shown in the reference schematic,
Figure 2-9
serial port example, below. The
transceiver shown in the reference schematic is of type Exar, part number SP336. This
transceiver is a multiprotocol RS232, RS485, RS422 transceiver. Single protocol transceivers
may be used as required. The xPico interface may also be directly connected to the UART
interface of an external CPU. Serial Port 2 is a three wire interface only. It operates like Serial
Port 1, except it does not support hardware Flow Control (i.e. no RTS/CTS) and modem control
(i.e. no DTR/DCD). It is highly recommended to connect RTS and CTS for serial port 1.
Table 2-8 xPico 110 Serial Port Signals
Signal
Pin
Description
Reset State
TXD1
57
Serial Transmit Data output
Output
RTS1
55
Serial Ready-to-Send / Serial Transmit enable
Output
RXD1
56
Serial Receive Data input
Input
CTS1
54
Serial Clear-to-Send
Input
TXD2
53
Serial Transmit Data output 2
Output
RXD2
52
Serial Receive Data input 2
Input
