CHAPTER 1
INTRODUCTION

The PCCOM ISA bus 2 port RS422/RS485 adapter provides two asynchronous serial communication ports, which enables one computer to communicate with other computers via communication lines, or to link the computer and serial peripheral devices such as terminals, modems, serial printers, plotters, ... etc.

The PCCOM ISA bus 2 port RS422/RS485 adapter may be configured with up to two individually addressable RS422/485 ports and individually interruptible for any PC/AT, PC/386, PC/486, Pentium or compatible system. It can be addressed anywhere within the full range of PC I/O ports and each port address can be set individually as your requirement. The interrupt selection feature provides individual interrupt selection for each port, so that you can arrange the 2 ports in any combination of interrupt you need.

The PC COM ISA bus 2 port RS422/RS485 adapter provides signal drivers and receivers, which can be set by software or hardware. Since the adapter support differential communication lines, it provides longer and more reliable communication quality than does RS232. The communication speed is up to 460K baud and the maximum transmission distance is up to 4000 ft.

Under the RS422 mode, RTS and CTS are used to provide communication flow control protocol. Under he RS485 mode, only transmission and receive signal are used, both drivers and receivers can be enabled or disabled by jumper setting or software. This means the RS485 provides a multi-point communication protocol.

The PCCOM ISA bus 2 port RS422/RS485 board can be used to plug in 8250, 16450, 16550, or 16650 chips, and the PCCOM device driver can detect it automatically. There are two kinds of communication speed can be choose, one is normal speed mode that its baud rate up to 115200, another is high speed mode that its baud rate up to 460K.

When set the PCCOM board to RS422 mode, it is particularly suited to facilitate the connection of terminals (VDUs) in multi-user operating systems.