Electrical computers and digital data processing systems: input/ – Input/output data processing – Transfer direction selection
Reexamination Certificate
1998-08-10
2001-02-20
Dinh, Dung C. (Department: 2757)
Electrical computers and digital data processing systems: input/
Input/output data processing
Transfer direction selection
C710S032000, C709S217000, C709S227000
Reexamination Certificate
active
06192423
ABSTRACT:
BACKGROUND
The present invention concerns remote management of a computer system and pertains particularly to sharing a single serial port between system remote access software and a remote management microcontroller.
Network servers are increasingly being managed remotely. Management is typically performed using remote access software running on the network server. A remote user can access the remote access software through a network connection. The network connection could be, for example through a 10 Base-T or 100 Base-T connection. Alternatively, the remote user can access the remote access software running on the network server by connecting through a public telephone network to a modem which is connected to the network server.
However, when an operating system is down (i.e., the operating system is not running), it is generally not possible to utilize the remote access software. For this purpose, some network servers utilize a separate microcontroller. The microcontroller can provide the remote user with troubleshooting data and access to the server console. Once the operating system is up and running, the remote access software provides the remote user with more functionality for management of the network server.
Typically, a network server will utilize two telephone lines, each telephone line with a dedicated modem. One telephone line is used when the remote user connects to the remote access software, and the other telephone line is used with the remote user connects to the separate microcontroller. However, there can be a significant overhead cost to maintain two modems and two telephone lines for remote management.
In order to reduce this overhead, there have been attempts to design a network server so that remote access software and a separate microcontroller share a single modem and single telephone line. See for example, IBM PC Server, Advanced Systems Management Adapter Installation Instructions, Available as part Number 05L1467 from IBM, September 1997, pp. 23-27. See also, Integration & Management; Remote Server Management with Integrated Remote Console, available on the internet from Compaq, October 1996. However, these solutions have tended to be clumsy to use and/or unreliable.
BRIEF SUMMARY OF THE INVENTION
In accordance with the preferred embodiment of the present invention, a serial port is shared by a microcontroller and a host application. The microcontroller initially responds to a remote user making connection to the serial port. Upon the remote user requesting connection to the host application, a hardware switch connects a serial port connector to serial port hardware utilized by the host application. The connection between the remote user and the host application is monitored, so that when the connection between the remote user and the host application is discontinued, the serial port connector is reconnected to the microcontroller.
For example, the switching is accomplished using a multiplexer and the monitoring is performed by control logic separate from the microcontroller. In the preferred embodiment, the serial port is RS-232 compatible. The control logic monitors a data carrier detect line (DCD), a data terminal ready line (DTR) and a receive data line (RD) of the serial port to determine when the connection between the remote user and the host application is discontinued. Also in the preferred embodiment, the host application is a remote access software running on a network server.
The present invention provides for reliable sharing of a serial port. Since the switching is done in hardware, the solution presented does not hang when there are software errors.
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Dinh Dung C.
Hewlett--Packard Company
Trim Nkosi N
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