THE PCI-COM422 and 485/8 Series serial adapters available from Interworld Electronics have baud rates up to 460.8kbps and come with an 8-DB9 male fan-out cable. The model PCI-COM422/8 supports RS422 communications and the model PCI-COM485/8 supports RS485 communications.
The cards feature eight independent, asynchronous RS422 or RS485 serial ports with 16550 UARTs. The 16550 UART's include a 16-byte transmit/receive buffer to protect against lost data in multitasking operating systems, while maintaining 100 per cent compatibility with the original PC serial port.
Both cards utilise differential balanced drivers for long range and noise immunity. In case of communication conflict, the driver/receivers features thermal shutdown.
The cards support biasing by default and support termination by jumpers on the card. PCI-COM422/8 supports full-duplex and half-duplex communications with a four-wire cable connection. It also has the capability to add load resistors to terminate the communication lines.
Receiver inputs at each end of the network should be terminated to eliminate "ringing". The RS-485 operation on the PCI-COM485/8 involves switchable transceivers and the ability to support multiple devices on a single part line.
The number of devices served on a single line can be expanded from the RS485 specification of 32 by the use of repeaters such as the QT485OP or QTM-8510, also from Interworld Electronics.
The PCI-COM485/8 card automatically controls the RS-485 driver enabled signal. This auto-enable functionality, where the driver is controlled by hardware rather than through software, makes the PCI-COM485/8 card ideal for use in multi-tasking systems such as Windows 95/98/NT/2000. Interworld Electronics 03 9563-5011.