Simultaneous communication method and system

• US 4,896,151 A
• Filed: 10/26/1987
• Issued: 01/23/1990
• Est. Priority Date: 10/28/1986
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sakata, Masahiro, Kuranami, Shoubu
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Pudpud, E. O.
• Application Number:
  US07/112,212
• Time in Patent Office: 820 Days
• Field of Search: 340/825.52, 340/825.06, 371/33, 371/32, 370/60, 370/94, 370/85, 375/7
• US Class Current: 370/445
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling

Abstract

In a simultaneous communication as in a POS system in which the same data including a multiplicity of data blocks is transmitted from a controller to a multiplicity of terminals all at once, the controller transmits all of the data blocks to the terminals without receiving any acknowledgement from each of the terminals in the course of data transmission. Each time the data block is received, the terminals hold information concerning the acknowledgement of the data block. After the termination of transmission of the whole of the data, the controller receives the acknowledgement information from each terminal into a management table. Based on the contents of the mangement table, the controller retransmits the data to a terminal(s) indicative of a negative acknowledgement in a similar manner to the above-mentioned data transmission or while taking acknowledgement for each data block.

Claims

1. A simultaneous communication method of transmitting data, inclusive of a plurality of data blocks, in a local network in which the frequency of occurrence of transmission error is low, from a controller to a plurality of terminals all at once, comprising the steps of:

(a) transmitting the data blocks of said data in sequence from said controller simultaneously to all of said plurality of terminals;

(b) holding in each of said terminals a respective acknowledgement response for each data block; and

(c) successively sending a single acknowledgement response from each of said terminals to said controller only upon termination of transmission of all of the data blocks of said data, said single acknowledgement response from each terminal indicating whether any data block in the data received by said terminal is erroneous data;

wherein said controller retransmits all of the data on the basis of the acknowledgement response received from said terminals at least to ones of said terminals indicating a need for data retransmission, and said terminals which receive said retransmission send an acknowledgement response after each retransmission of one data block.

2. A simultaneous communication method according to claim 1, wherein said steps (a) and (b) are repeated on the basis of the acknowledgement response from said terminals for those terminals indicating the necessity of data retransmission.

3. A simultaneous communication method according to claim 2, wherein said controller discontinues the data retransmission to a terminal indicating the necessity of data retransmission when the number of times of data retransmission to that terminal exceeds a predetermined number, and said controller terminates its data transmission operation when an acknowledgement of correct receipt of said data is received from said terminals.

4. A simultaneous communication method according to claim 1, wherein said data has a data length in the order of 1 M byte and each of the data blocks has a block length in the order of 500 bytes.

5. A simultaneous communication system for transmitting data, inclusive of a plurality of data blocks, in a local network in which the frequency of occurrence of transmission error is low, from a controller simultaneously to a plurality of terminals, comprising:

transmission designating means provided in said controller for transmitting said plurality of data blocks in sequence simultaneously to all terminals;

response information holding means provided in each of said terminals for generating response information for each reception of one data block by that terminal and for holding the response information; and

means for transmitting to said controller from each terminal a single response signal indicating whether the response information held in said response information holding means in the respective terminal includes an error indication only when information indicative of the termination of data transmission of all of said plurality of data blocks is detected in the respective terminal;

wherein said controller includes response management memory means for receiving and storing the response signals from said terminals, and means responsive to the contents of said response management means for performing retransmission of the data to at least one of said terminals which indicates an unsuccessful response and said terminals include means responsive to receipt of retransmitted data for sending a response signal to said controller after each receipt of a data block.

6. A simultaneous communication method of transmitting data, inclusive of a series of data blocks, in a local network in which the frequency of occurrence of transmission error is low, from a controller to a plurality of terminals all at once, comprising the steps of:

(a) transmitting a series of data blocks of said data from said controller to said plurality of terminals without receiving an acknowledgement for each data block, each terminal temporarily holding information representing acknowledgement and negative acknowledgement for each data block;

(b) successively sending to said controller a respective information signal from each terminal representing whether a negative acknowledgement is held in the respective terminal upon termination of transmission of said series of data blocks; and

(c) effecting retransmission of the entire series of data blocks by said controller in response to an information signal representing negative acknowledgement and sending an information signal from a terminal receiving retransmitted data after receipt of each retransmitted data block.

7. A simultaneous communication method according to claim 6, wherein said controller retransmits said series of data blocks when receiving an information signal from a terminal indicating negative acknowledgement upon each retransmission of one data block.

8. A simultaneous communication method according to claim 6, wherein said steps (a) and (b) are repeated each time the controller receives negative acknowledgement from said terminal, until the repetition reaches a given number of times.

9. A simultaneous communication method according to claim 8, wherein said controller discontinues the data retransmission to the terminal indicating the necessity of data retransmission when the number of times of data retransmission to that terminal exceeds a predetermined number, and said controller terminates its data transmission operation when responses indicative of the success of acknowledgement of said same data are received from the remaining terminals.

10. A simultaneous communication method according to claim 6, wherein said data has a data length in the order of 1 M byte and each of the data blocks has a block length in the order of 500 bytes.

11. A POS system according to claim 6, wherein said communication line is a local area network and said message block includes at least a price look-up table.