MM MHUBX8

Description

The MHUBX8 is an 8-port automatic RS485 repeater hub (non-isolated) with a master RS232/RS485 port. The unit can be used to expand RS485 serial communications networks by increasing the maximum distance and/or number of nodes. Data received by the master port is transmitted to all eight distribution ports (CHA thru CHH). Data received into a distribution port is transmitted out the master port, but is NOT transmitted out any other distribution port. Each distribution port has its own termination jumper and an RXEN (receive enable) jumper. Bias is fixed with 620 Ohms of pull-up and pull-down resistance to hold the data lines in a known state when the data lines are inactive. Each distribution port on the MHUBX8 hub will support up to 32 full-load RS485 devices. Additional units/nodes can be added, using 1/2(64 units) and 1/4(128 units) load devices. The SP485EEP transceiver IC, employed in the MHUBX8, is a 1 load device, has built-in 22-OHM protection resistors, and is capable of communicating at speeds up to 230.4Kbps++ using the RS485 master port and 115.2Kbps using the RS232 master port. Speeds up to 921.6Kbps are possible using the RS485 master port with about a 25uSec turn around delay from transmit to receive mode.