US 4,377,852 AGranted

Terminal emulator

AssigneeTexas Instruments Incorporated

InventorE. Earle Thompson

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Abstract

A communications control system for enabling a small computer system, such as a personal computer, to emulate a terminal and thus to communicate with a remote system. Incoming data from the remote system is entered into a circular buffer on an interrupt basis. The communications control system alternately scans the circular buffer for newly entered data and the keyboard for operator generated messages. Any control characters are decoded and appropriate actions taken. Received alphanumeric characters are stored in a display memory for video display and in a system RAM for later retrieval and study. The display memory is optionally loaded in an intelligent wrap mode in which words are not broken on wrap around or a non-wrap mode which preserves the columns of the data as originally received. Scrolling controls enable the operator to enter a desired portion of the data stored in the system RAM into the display memory for viewing in either wrap-on or wrap-off modes. This invention also provides control of data transfer to and from the received line memory and local peripherals. In the preferred embodiment, the system is embodied by a plug in ROM module used with a compatible personal computer.

Claims25

Dependent claims

A plug-in communications control program module for use in a digital computing system including a central processing unit, a communications interface means, a memory means, a video display system and a plug-in type port for temporarily receiving a plug-in program control module, said plug-in communications control module comprising:

a connector means connectable to said plug-in type port;
and
a solid state read only memory means having permanently stored therein a control program for interaction with said central processing unit of said digital computing system, said central processing unit and said plug-in communications control module together comprising (a) means for defining said memory means into at least a temporary data input buffer, a display memory means and a received line memory means having a greater size than said display memory means, (b) means for storing data characters received by said communications interface means in said temporary data input buffer, (c) means for periodically determining if at least one data character has been stored in said temporary data input buffer, (d) means for reading data characters out of said temporary data input buffer when it has been determined that at least one data character has been stored in said temporary data input buffer until all data characters stored in the temporary data input buffer have been read out, (e) means for storing data characters read out of said temporary data input buffer in said display memory means in a predetermined sequence, and (f) means for storing data characters read out of said temporary data input buffer in said received line memory means in sequential memory locations as said data characters are read out.

A communications control system comprising:

a central processing unit for performing data processing functions under program control;
a memory means including a temporary data input buffer, a display memory means having a plurality of memory locations for storing data characters therein and a received line memory means having a plurality of sequential memory locations, greater than the number of memory locations in said display memory means, for storing data characters therein;
a communications interface means connectable to a communications line for receiving communications signals from said communications line and storing data characters corresponding to received communications signals in said temporary data input buffer;
a video display means for displaying a matrix of alphanumeric characters corresponding to the data characters stored in said display memory means;
a scrolling control means for receiving operator generated scrolling control signals;
a plug-in type port;
and
a plug-in communications control module having a connector means connectable with said plug-in type port and a solid state read only memory means having a control program permanently stored therein, said central processing unit and said plug-in communications control module together comprising:
(a) means for periodically determining if at least one character has been stored in the temporary data input buffer;
(b) means for reading data characters out of the temporary data input buffer when it has been determined that at least one data character has been stored in the temporary data input buffer until the last data character stored in the temporary data input buffer has been read out;
(c) means for storing data characters read out of said temporary data input buffer in the display memory means in a predetermined sequence;
(d) means for storing data characters read out of said temporary data input buffer in the received line memory means in said sequence of memory locations as said data characters are read out;
and
(e) means for storing a subset of the data characters stored in the received line memory means in the display memory means, said subset being determined by said scrolling control signals.

11 more elements

A digital communications system comprising:

a central processing unit for performing data processing functions under program control including an interrupt means for interrupting the performing of a program controlled function and performing a priority function;
a memory means including a circular interrupt buffer having a plurality of circularly sequential memory locations, a display memory means having a plurality of memory locations and a received line memory means having a plurality of memory locations, greater than the number of memory locations of said display memory means;
a video display means for displaying a matrix of alphanumeric characters corresponding to the data characters stored in said display memory means;
a plug-in type port;
a plug-in control module having a connector means connectable to said plug-in type port and a read only memory means including a control program permanently stored therein, said central processing unit and said plug-in control module together including (1) means for periodically determining if at least one data character has been stored in said circular interrupt buffer, (2) means for reading out data characters from said circular interrupt buffer one at a time in said circular sequence when it is determined that at least one data character has been stored in said circular interrupt buffer until the last data character stored in said circular interrupt buffer has been read out, (3) means for storing data characters read out of said circular interrupt buffer in said display memory means in a predetermined sequence, (4) means for storing data characters read out of said circular interrupt buffer in said received line memory means in said sequence of memory locations as said data characters are read out, and (5) means for storing a subset of the data characters stored in said received line memory means in said display memory means;
a communications interface means connected to said interrupt means of said central processing unit including (1) means for receiving an electrical signal from a communications transmission line, (2) means for generating a data character corresponding to said received electrical signal according to a predetermined code and (3) means for interrupting the program controlled function of said central processing unit and causing said central processing unit to perform the priority function of storing said generated data character in said circular interrupt buffer in a memory location after the memory location of the last stored data character according to said circular sequence;
and
a scrolling control means for receiving operator generated scrolling control signals, said scrolling control signals controlling said subset of data characters stored in said display memory means.

5 more elements

Dependencies are inferred from the claim text.