Serial Communications Extension Host (SCEH)

The Serial Communications Extension Host (SCEH) is a Delta 2000/P-based communications device with Linux port which offers a low-cost, highly flexible communications “black box” for providing virtual serial connections between legacy devices via Ethernet. Many single-board systems exist which perform similar functions as the SCEH, but the SCEH adds the ability to communicate asynchronously and synchronously in RS-530, RS-423, and RS-232 modes. This communication is directed to nodes designated by the user during setup, and it allows for user specified service port numbers in a private network. For networks attached directly to the Internet, the port number 16360 must be used since it is the registered port for this service. Hardware line control is optional, as well as buffer size up to 512 bytes. The SCEH hardware design is based on the Motorola MPC855 processor, which includes a low-speed (max. 19.2 Kbps) console port and a 10 Base-T/100 Base-T Ethernet connection. LEDs are visible to indicate serial and Ethernet activity.

The SCEH may be configured via the local console connection, allowing the operator to configure operational parameters for the serial connections. SCEH configuration is implemented through variables stored in the NVRAM of the SCEH. These variables define the circuit type for the SCEH and operating parameters for the Serial Communications Port and the network. A Console Monitor program provides access to the variables and has additional commands for use during testing of configurations. Physical access to the Console Monitor program allows absolute control over the SCEH and its configuration. Portions of the SCEH NVRAM variables are accessible from SNMP management software via the SCEH SNMP agent. This feature allows the more dynamic variables to be changed over the network, without need for access to the SCEH console. A security switch is provided to prevent further configuration. In addition to the configuration tools, a simple debug monitor can be provided on the optional console port to facilitate unit debug and installation.

APPLICATIONS

The principal application of the SCEH is to extend serial communications over an Ethernet Network. Using the SCEH, “virtual serial” connections can be established between legacy instruments connected to the network. The SCEH will maintain synchronization between these legacy instruments via the Ethernet.