COMMUNICATION MULTIPLEXER FOR ONLINE DATA TRANSMISSION

• US 3,573,740 A
• Filed: 07/03/1968
• Issued: 04/06/1971
• Est. Priority Date: 07/03/1968
• Status: Expired due to Term

• Current Assignee: Bob J. Baker, Melvyn S. Berger
• Original Assignee: Bob J. Baker, Melvyn S. Berger
• Inventors: Berger, Melvyn S., Baker, Bob J.
• Application Number:
  US04/742,354
• Time in Patent Office: 1,007 Days
• US Class Current: 710/31
• CPC Class Codes: G06F 13/22 using successive scanning, e.g. polling G06F13/24 takes precedence

Abstract

A communications system comprised of a multiplexer and a plurality of unit adapters for transferring data characters between a high speed digital computer and a plurality of relatively low speed data transmission devices operating online with the computer. A scanner circuit included in the multiplexer provides for sequential servicing, in turn, each of the unit adapters for transferring the data characters. The scanner circuit may be interrupted at any time such that the computer can transfer a function selector character to any of the unit adapters, the character determining whether the unit adapter will thereafter operate in an input or output mode. Monitor and control logic in each unit adapter has circuitry therein for detecting an overload condition resulting from online operation of the computer system during an input mode of operation, thereby detecting any loss of data in its real time operation and enabling the computer to monitor the circuits to correct the loss of data caused by the overload condition.

Claims

1. A communications system for transferring data between a computer and a plurality of remote data terminals, comprising:

a plurality of unit adapters, each connected to one of said remote data terminals and each capable of being operated in an input or output data transfer mode;

a common channel for transferring data between any selected one of said unit adapters and said computer;

a register responding to control data from said computer for connecting any selected one of said unit adapters to said common channel;

means for transferring control data from said computer through said common channel to a unit adapter selected by the register for setting up the mode of operation of said unit adapter; and

a scan counter capable of operatively connecting each of said unit adapters, in turn, to said common channel, for transferring data therethrough in accordance with the transfer mode of the respective unit adapters.

2. The invention in accordance with claim 1 wherein storage means are included in each of said unit adapters for temporarily storing data being transferred therethrough.

3. The invention in accordance with claim 1 including monitor means in each of said unit adapters for sensing an input data transfer overload condition therein and causing a status signal to be transferred over the common channel to the computer at the time the unit adapter is operatively connected thereto by the scan counter.

4. The invention in accordance with claim 1 wherein a unit adapter has been set to operate in an input data transfer mode, and wherein said unit adapter includes a first and second storage means, said first storage means for storing data received from the remote data terminal;

transfer means for transferring data from said first to said second storage means; and

monitor means for sensing when both said first and second storage means are storing input data and causing a status signal indicative of an overload condition to be transferred over the common channel to the computer at the time the unit adapter is operatively connected thereto by the scan counter.

5. A communications system for transferring data between a computer and a plurality of remote data terminals, comprising:

a plurality of unit adapters, each connected to one of said remote data terminals and capable of being operated in an input or output data transfer mode;

a common channel for transferring data between any selected one of said unit adapters and said computer;

a register capable of being arbitrarily set to provide output address signals to connect any selected one of said unit adapters to said common channel;

means responding to control data from said computer for setting said register and for transferring control data through said common channel to the selected unit adapter for setting the mode of operation thereof; and

a scanning counter providing output address signals for interrogating each of said unit adapters, in turn, to detect if a return signal from one of said unit adapters is ready to transfer data, including means for operatively connecting each unit adapter in a ready condition to said common channel, for transferriNg data therethrough in accordance with its transfer mode.

6. The invention in accordance with claim 5, wherein a unit adapter has been set to operate in an output data transfer mode;

and wherein circuit means are provided for transferring output address signals of the scanning counter to the compute when said return signal from said unit adapter is detected to be ready to transfer data.

7. The invention in accordance with claim 5, wherein a unit adapter has been set to operate in an input data transfer mode;

and wherein circuit means are provided for transferring the output address signals of the scanning counter to the computer when said return signal from said unit adapter is detected to be ready to transfer data.

8. The invention in accordance with claim 5, including address decoder means responsive to the output address signals provided by one of said register and said scan counter for operatively connecting any selected one of said unit adapters to said common channel.

9. A communications system for transferring data between a computer and a plurality of remote data terminals, comprising:

a plurality of unit adapters, each connected to one of said remote data terminals and each initially set to operate in an input or output data transfer mode;

a common channel for transferring data between a selected one of said unit adapters and said computer;

a scanning counter capable of cyclically operating to connect each of said unit adapters, in turn, to said common channel, for transferring data therethrough in accordance with its transfer mode; and

register means capable of interrupting the counting action of said scanning counter at any count of its cycle and connecting said common channel to a selected one of said unit adapters for changing the data transfer mode thereof, in response to control data from said computer, said scanning counter then resuming its cyclical operation of connecting each of said unit adapters, in turn, to said common channel, by starting with the unit adapter identified by the count of the scanning counter at the time it was interrupted.

10. The invention in accordance with claim 9, wherein each said unit adapter includes a buffer register means for temporarily storing data being transferred in series to or from its connected remote data terminal.

11. A communications multiplexer system for transferring data characters between a computer and a plurality of remote data terminals, comprising:

a plurality of unit adapters, each connected to a remote terminal and means enabling each to be set to transfer a data character in an input or output transfer mode in response to a function character transferred to the unit adapter from the computer;

a multiplexer circuit capable of being selectively gated to each of said unit adapters for transferring data characters between the computer and said remote terminals in accordance with the transfer mode of each unit adapter;

scanner means included in said multiplexer circuit for gating in an ordered sequence each of said unit adapters ready to effect the transfer of data characters therethrough; and

control means included in said multiplexer circuit and responding to control data from the computer for interrupting the gating in an ordered sequence of each of said unit adapters in order to gate a function character from the multiplexer to a particular one of said unit adapters, said control means included in said multiplexer circuit including means enabling resumption of the gating in an ordered sequence of each of said unit adapters following the transfer of the function character from the multiplexer to the particular one of said unit adapters.

12. A communications system for transferring data between a computer and a plurality of remote data terminals, comprising:

a plurality of unit adapters, each connected to one of said remote data terminals and each capable of operating in an input or output data transfer mode;

a common channel for transferring data between any selected one of said Unit adapters and said computer;

a register responding to control data from said computer for connecting any selected one of said unit adapters to said common channel;

means for transferring control data from said computer through said common channel to a unit adapter selected by said register for setting up the mode of operation of said unit adapter;

a scan counter providing output address signals for sequentially interrogating each of said unit adapters; and

control means for temporarily stopping said scan counter when an interrogated unit adapter is detected to be in a condition to transfer data and for operatively connecting said unit adapter to said common channel for transferring data therethrough in accordance with the transfer mode of the respective unit adapter.

13. The invention in accordance with claim 12, wherein circuit means are provided to transfer the output address signals of the scan counter to the computer when a unit adapter is detected that is in a condition to transfer data.

14. In a real-time communications system for transferring data characters provided by each of a plurality of remote data terminals at a relatively slow, random rate to a high speed digital computer, comprising:

a plurality of unit adapters, each capable of temporarily storing a data character received at a random rate from one of said remote data terminals;

a common channel for transferring a data character from any selected one of said unit adapters to said computer;

a cyclically operated scan counter whose count output identifies each of said unit adapters for sequentially interrogating each of said unit adapters, in turn, at a high rate; and

means for temporarily holding the count output of said scan counter each time a unit adapter is detected to be storing a data character to enable said unit adapter to transfer the data character through said common channel to said computer.

15. The invention in accordance with claim 14, including means for transferring along with the transfer of a data character to said computer, the count output of the scan counter that identifies the unit adapter supplying the data the scan

16. In a real-time communications multiplexer system for transferring a different multicharacter data message from each of a plurality of remote data terminals, said messages being transferred one character at a time in an interleaved manner to a high speed digital computer, comprising:

a plurality of unit adapters, each capable of temporarily storing one of the data characters of the message being recieved in a random rate from one of said remote data terminals;

a multiplexer capable of transferring data characters of the messages, in an interleaved manner, as received one at a time from different ones of said unit adapters;

a cyclically operated scan counter whose count output identifies each of unit adapters for sequentially interrogating each of said unit adapters, in turn, at a high rate;

circuit means for temporarily holding the count output of said scan counter when a unit adapter is detected to be storing a data character of a message being received from a data terminal, to enable said unit adapter to transfer the data character through said multiplexer to said computer; and

further circuit means responsive to the count output of said scan counter to identify each data character being transferred in an interleaved manner through the multiplexer as being a part of the message being received from one of said remote data terminals.