FEATURES

		RS-422/485 interface card for IBM PC
		Configurable as RS-422 or RS-485 communication protocol
		Fully optically isolated to the PC system
		High speed opto isolator and fully isolated DC/DC converter provides high isolation between the communication line and the PC system
		IBM PC RS-232 software compatible
		Up to two PX-2285A can be installed in a single computer system to enable addressing 4 RS-422/RS-485 ports simultaneously

DESCRIPTION

This adapter is designed for the 8088/86, 80286, 80386, 80486 and 80586 based computers. It contains one or two asynchronous communication ports using the standard RS-422/RS-485 interface. Each asynchronous communication can add and remove a start bit, parity bit, and 1 to 2 stop bits. Baud-rates are programmable from 50 baud to 115,200 baud; supporting 5-, 6-, 7-, and 8-bit characters with 1, 1-1/2, or 2 stop bits. The adapter COM port addresses and interrupts are DIP switch-selectable to MS-DOS COM1 - COM4. Configuring COM port address to other than COM1, COM2 for additional RS-232 communication channels is also supported. Up to four PX-2285A-2 adapters can be installed in a single computer system. The board can be installed into any 8-bit or 16-bit PC/AT I/O expansion slot. Shipped with the adapter is this instruction manual, this manual provides detailed technical information and data sheets outlining specifications.

MODEL NUMBER

Model No.	Description
PX-2285A-1	One port RS-422/485 communication card (16450 USART)
PX-2285A-2	Two ports RS-422/485 communication card (16450 USART)
PX-2285A-1A	One port RS-422/485 communication card (16550 USART)
PX-2285A-2A	Two ports RS-422/485 communication card (16550 USART)

FUNCTIONAL DESCRIPTION

This card contains one or two asynchronous communication ports using the standard RS-422/RS-485 interface. The adapter COM port addresses and interrupts are DIP switch-selectable to MS-DOS COM1/COM2/COM3/COM4 addresses and interrupts. Configuring COM port address to other than COM1, COM2 for additional RS-232 communication channels is also supported. Up to two PX-2285A-2 adapters can be installed in a single computer system. RS-232 Interface The RS-232 interface is a very common one to one communication interface I/F. This means that if one station wants to connect to several stations, it requires the same number of RS-232 communication I/F as number of stations. A typical RS-232 I/F has at least 3 signals. These are the Signal Ground, the TX and the RX. The TX sends data from one station to another station. The RX receives data from the transmitting station. RS-422 Interface The RS-422 Interface is similar to RS-232 interface except it is designed to be used in harsher environments. The difference between the RS-232 and RS-422 is the electronic signals. The RS-232 uses single-ended signals while the RS-422 uses differential signals. This means the RS-422 can transmit data at longer distances and with more stability than the RS-232 I/F. The RS-422 can be used in much noisier environments. However, like the RS-422, the RS-232 is for one on one communication. This means if a host computer wants to connect to several remote devices, it requires the same number of RS-422 communication lines as remote devices. A typical RS-422 I/F has at least 5 signals. These are the Signal Ground, the TX+, the TX-, the RX+ and the RX-. The TX+ and TX- send data from one device to another. The RX+ and RX- receive data from one device to another. RS-485 Interface The RS-485 I/F is similar to RS-422 I/F except it is a multiple access network. Unlike the RS-422, it uses the same wires to send and receive data. The benefit is : only one RS-485 I/F is required for a multiple station communication network. The RS-485 interface provides an economical solution for multiple station communication without the overhead of a LAN. However, because all data communication uses the same wires (TRX+ and TRX-), one must detect the communication line status first before sending any data. If the line is busy, it means a station is sending data to another station. The user must wait until the communication line is cleared before any message can be sent. A more detailed explanation regarding the multiple access protocol can be found in the next section. A typical RS-485 I/F has at least 3 signals. These are the Single Ground, the TRX+ and the TRX-.

BLOCK DIAGRAM

Specifications

Communication Protocol
No. of ports per card	2 (Max.)
Maximum data transfer distance	4000 feet
Baud rates	50 baud - 115,200 baud
Parity	None, Even or Odd
Data bits	5, 6, 7, or 8
Stop bits	1, 1.5, or 2
Interface protocol	EIA RS-422/485, DCE
Port signals	TX, RX, RTS, CTS, GND
Connector	9 pin D-type female
Communication controller	16450 or 16550
Output driver	SN75172
Input receiver	SN75173
Input resistance	>12K ohm
Termination resister	1K ohm
Clock input	1.8432MHz
Isolator	PC900V optical isolator
Interface Characteristics
Compatible bus	IBM PC or Compatibles
Data path	8-bit
Interface type	I/O mapped with 10-bit addressing
Number of locations occupied	8 I/O locations per port
Base address range	3F8H, 2F8H, 3E8H, 2E8H, 3E0H, 2E0H, 2D0H or 2C0H
Interrupt	IRQ2, 3, 4, 5, 10, 11, 12 or 15
Power requirement/consumption	+5V / 550 mA
Physical/Environmental
Operating temperature range	+5 ° C to +50 ° C
Storage temperature range	-25 ° C to +85 ° C
Operating humidity range	0 to 90% non-condensing
Storage humidity range	0 to 90% non-condensing
Dimensions	19.0 x 13.0 x 2.0 cm
Weight	165 g