User's Manual

PW2050 Embedded Device Server Integration Guide 19
signal levels on the serial interface are 3.3V tolerant. The serial interfaces require an external
transceiver in order to connect to external RS232, RS485, or RS422 networks. The signals of
the Serial Ports may be connected as shown in the reference schematic 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 PW2050 interface may also be directly connected to the UART
interface of an external CPU.
Table 2-5 PW2050 Serial Port Signals
Signal Module Pin Description
TXD1 83 Serial Transmit Data output
RTS1 81 Serial Ready-to-Send / Serial Transmit enable
RXD1 82 Serial Receive Data input
CTS1 80 Serial Clear-to-Send
TXD2 79 Serial Transmit Data output 2
RTS2 24 Serial Ready-to-Send / Serial Transmit enable
RXD2 78 Serial Receive Data input 2
CTS2 25 Serial Clear-to-Send
Table 2-6 Example RS232 Connections (Serial Transceiver Required)
PW2050 Signal DTE Connector DCE Connector
Signal (Logic) Description DB9 DB25 Signal DB9 DB25 Signal
RXDx Data In 2 3 RXDx 3 2 TXDx
TXDx Data Out 3 2 TXDx 2 3 RXDx
RTSx H/W Flow Control Output 7 4 RTSx 8 5 CTSx
CTSx H/W Flow Control Input 8 5 CTSx 7 4 RTSx
CPx Modem Control Input 1 8 DCDx 4 20 DTRx
CPy Modem Control Output 4 20 DTRx 1 8 DCDx
Table 2-7 Example RS422/485 Connections (Serial Transceiver Required)
PW2050
Signal (logic)
Description RS485
Signal
DB25 4
Wire
DB25 2
Wire
DB9 4
wire
DB9 2
wire
TXDx Data Out TX+485 14 14 7 7
TXDx Data Out TX-485 15 15 3 3
RXDx Data In RX+485 21 14 2 7
RXDx Data In RX-485 22 15 8 3
RTSx TX Enable
CPx RS485 Select
CPy RS485 2-wire