Digital data communication adapter

• US 4,168,469 A
• Filed: 10/04/1977
• Issued: 09/18/1979
• Est. Priority Date: 10/04/1977
• Status: Expired due to Term

• Current Assignee: NCR Corporation
• Original Assignee: NCR Corporation
• Inventors: Dharia, Prabodh M., Jenkins, Alfred D., Kurtz, John J., Patnaik, Haresh C., Parikh, Bipin D., Patel, Bhagubhai K., Mahajan, Prakash Y.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/839,548
• Time in Patent Office: 714 Days
• Field of Search: 179/15 R, 179/15 BA, 179/15 AL, 179/15 BV, 179/15 AP, 179/15 A, 179/2 DP, 178/50, 178/58, 340/147 C, 340/147 PC, 340/147 MD, 340/146.1 R, 364/200, 364/900
• US Class Current: 375/365
• CPC Class Codes: H03M 7/4025 constant length to or from Morse code conversion

Abstract

Communications between processor terminals are carried out through the use of communication adapters. Each adapter receives selected control signals for transmitting or receiving data over a serial communication link to or from a remote terminal. The transmission portion of an adapter includes pretransmission control circuitry which receives control signals and stores transmission control signals which are used to control the format and serial transmission of a frame of data to a remote terminal. Each frame of data is begun and terminated with a uniquely encoded flag byte. Following the first flag byte are successive address and control fields. An optional information field may follow the control field and may include encoded information designating a dynamic change in the byte size of the data. Immediately following the information field, a frame check sequence field, generated in accordance with the contents of each of the address, control, and information field, is transmitted, followed by a frame terminating flag byte.

In order to enable the adapter to receive a serial data stream from a remote terminal and couple this received data to its assoicated processor, the adpater includes pre-reception control and direct memory access control circuitry coupled over the common control bus to the common control module and its associated memory.

Upon completely disassembling a frame, the adapter generates appropriate status signals and an interrupt is supplied to the common control.

Claims

1. A method of controlling the transmission and reception of a frame of data in serial format, from a first processing terminal to at least one second processing terminal, respectively, comprising the steps of:

generating and transmitting at said first processing terminal, a sequence of groups of signals containing an address code identifying said at least one second processing terminal to which a data transmission is directed, prescribed control information, and data to be received by said at least one second processing terminal, respectively; and

within the group of signals containing the data to be received by said at least one second processing terminal, selectively generating

(i) a first sequence of signals representative of whether there is to be a change in the length of the data words,

(ii) a second sequence of signals representative of the number of data words prior to the occurrence of a word length change, and

(iii) a third sequence of signals containing each of said data words and address code change request data;

receiving, at said at least one second processing terminal, the sequence of groups of signals transmitted by said first processing terminal and, upon recognizing that the address code contained within said sequence of groups of signals identifies said at least one second processing terminal, causing said sequence of groups of signals to be disassembled in accordance with any change in data word size as represented by said first and second sequences of signals;

generating and transmitting, at said first processing terminal, a first group of signals representative of a prescribed function of said sequence of groups of signals;

generating and transmitting, at said first processing terminal, a pair of groups of flag signals each of which uniquely identifies an end point of a frame of data;

so that each frame of data transmitted from said first processing terminl to said at least one second processing terminal is comprised of an initial flag signal group, a sequence of address, control, and data signal groups, a prescribed function signal group, and a terminating flag signal group, a sequence of address, control, and data signal groups, a prescribed functional signal group, and a terminating flag signal group at said at least one second processing terminal, monitoring signals from a first processing terminal and, upon detecting an initial flag signal group, comparing the address signal group with at least one receiver address code identifying said at least one second processing terminal to determine whether or not the signals from a first processing terminal are being directed to said at least one second processing terminal; and

at said at least one second processing terminal, modifying said at least one receiver address code identifying said at least one second processing terminal, so that for a subsequently received frame of data, the address signal group transmitted from said first processing terminal will be compared with a new receiver address code identifying said at least one second processing terminal.

2. A method of controlling the transmission and reception of a frame of data in serial format, from a first processing terminal to at least one second processing terminal, respectively, comprising the steps of:

generating and transmitting at said first processing terminal, a sequence of groups of signals containing an address code identifying said at least one second processing terminal to which a data transmission is directed, prescribed control information, and data to be received by said at least one second processing terminal, respectively;

within the group of signals containing the data to be received by said at least one second processing terminal, selectively generating

(i) a first sequence of signals representative of whether there is to be a change in the length of the data words,

(ii) a second sequence of signals representative of the number of data words prior to the occurrence of a word length change, and

(iii) a third sequence of signals containing each of said data words;

receiving, at said at least one second processing terminal, the sequence of groups of signals transmitted by said first processing terminal and, upon recognizing that the address code contained within said sequence of groups of signals identifies said at least one second processing terminal, causing said sequence of groups of signals to be disassembled in accordance with any change in data word size as represented by said first and second sequences of signals;

generating and transmitting, at said first processing terminal, a first groups of signals representative of a prescribed function of said sequence of groups of signals;

generating and transmitting, at said first processing terminal, a pair of groups of flag signals each of which uniquely identifies an end point of a frame of data;

so that each frame of data transmitted from said first processing terminal to said at least one second processing terminal is comprised of an initial flag signal group, a sequence of address, control, and data signal groups, a prescribed function signal group, and a terminating flag signal group at said at least one second processing terminal;

monitoring signals from a first processing terminal and, upon detecting an initial flag signal group, comparing the address signal group with at least one receiver address code identifying said at least one second processing terminal to determine whether or not the signals from a first processing terminal are being directed to said at least one secured processing terminal;

also at said at least one second processing terminal, selectively separating a received frame of data into its respective signal groups and generating a second group of signals representative of a preselected function of the received sequence of groups of signals; and

comparing the first group of signals representative of said prescribed function of said sequence of groups of signals transmitted from a first processor terminal with said second group of signals representative of said preselected function of the received sequence of groups of signals, whereby the correlation of the received frame with that transmitted can be determined.

3. A method according to claim 2, further comprising the steps of, at said at least one second processing terminal, detecting said terminating flag signal group and thereby detecting the termination of a received frame of data.

4. A method according to claim 2, further comprising the step of, at said at least one second processing terminal, monitoring the length of the frame of data and generating an invalid frame indicating signal upon recognition of a terminating flag signal group prior to the length of the monitored frame of data reaching a preselected value.

5. A method of controlling the transmission and reception of a frame of data in serial format, from a first processing terminal to at least one second processing terminal, respectively, comprising the steps of:

generating and transmitting at said first processing terminal, a sequence of groups of signals containing an address code identifying said at least one second processing terminal to which a data transmission is directed, prescribed control information, and data to be received by said at least one second processing terminal, respectively; and

within the group of signals containing the data to be received by said at least one second processing terminal, selectively generating

(i) a first sequence of signals representative of whether there is to be a change in the length of the data words,

(ii) a second sequence of signals representative of the number of data words prior to the occurrence of a word length change, and

(iii) a third sequence of signals containing each of said data words; and

receiving, at said at least one second processing terminal, the sequence of groups of signals transmitted by said first processing terminal and, upon recognizing that the address code contained within said sequence of groups of signals identifies said at least one second processing terminal, causing said sequence of groups of signals to be dissassembled in accordance with any change in the data word size as represented by said first and second sequences of signals;

generating and transmitting, at said first processing terminal, a first group of signals representative of a prescribed function of said sequence of groups of signals;

generating and transmitting, at said first processing terminal, a pair of groups of flag signals each of which uniquely identifies an end point of a frame of data;

so that each frame of data transmitted from said first processing terminal to said at least one second processing terminal is comprised of an initial flag signal group, a sequence of address, control and data signal groups, a prescribed function signal group, and a terminating flag signal group;

at said first processing terminal,

selectively modifying said sequence of groups of signals and said first group of signals so as to prevent the frame of data from containing groups of signals corresponding to said flag signals other than at those portions of a data frame where flag signals are intended to occur, and

at said at least one second processing terminal,

detecting the occurrence of any selective modification of the sequence of groups of signals and said first group of signals transmitted from a first processing terminal and removing said selective modification thereof so as to permit accurate disassembly of a frame of data received at said at least one second processing terminal.

6. A method according to claim 5, further comprising the steps of,

at said first processing terminal,

generating an abort character made up of a prescribed group of signals representative of the aborting of a frame, in response to the occurrence of prescribed conditions, and transmitting said abort character to said at least one second processing terminal, and

at said at least one second processing terminal,

detecting an abort character transmitted from a first processing terminal and thereby terminating frame reception.

7. A method according to claim 6, wherein the generation and transmission of an abort character at a first processing terminal comprises the generation and transmission of a unique group of signals as an abort character while inhibiting the selective modification of said sequence of groups of signals and said first group of signals.

8. A method of controlling the transmission and reception of a frame of data in serial format, from a first processing terminal to at least one second processing terminal, respectively, comprising the steps of:

generating and transmitting at said first processing terminal, a sequence of groups of signals containing an address code identifying said at least one second processing terminal to which a data transmission is directed, prescribed control information, and data to be received by said at least one second processing terminal, respectively; and

within the group of signals containing the data to be received by said at least one second processing terminal, selectively generating

(i) a first sequence of signals representative of whether there is to be a change in the length of the data words,

(ii) a second sequence of signals representative of the number of data words prior to the occurrence of a word length change, and

(iii) a third sequence of signals containing each of said data words; and

receiving, at said at least one second processing terminal, the sequence of groups of signals transmitted by said first processing terminal and, upon recognizing that the address code contained within said sequence of groups of signals identifies said at least one second processing terminal, causing said sequence of groups of signals to be disassembled in accordance with any change in data word size as represented by said first and second sequences of signals;

generating and transmitting, at said first processing terminal, a first group of signals representative of a prescribed function of said sequence of groups of signals;

generating and transmitting, at said first processing terminal, a pair of groups of flag signals each of which uniquely identifies an end point of a frame of data;

so that each frame of data transmitted from said first processing terminal to said at least one second processing terminal is comprised of an initial flag signal group, a sequence of address, control, and data signal groups, a prescribed function signal group, and a terminating flag signal group;

at said first processing terminal,

generating an abort character made up of a prescribed group of signals representative of the aborting of a frame in response to the occurrence of prescribed conditions, and transmitting said abort character to said at least one second processing terminal, and

at said at least one second processing terminal,

detecting an abort character transmitted from a first processing terminal and thereby terminating frame reception.

9. A data communication system for controlling the transmission and reception of a frame of data in serial format, from a first processing terminal whereat data to be transmitted is read out from a selectively addressable memory, said frame being comprised of a sequence of signal containing address, control, and data information fields, to at least one second processing terminal whereat received data is written into a selectively addressable memory, comprising:

at said first processing terminal,

first means for generating a first sequence of groups of signals containing the address of said at least one second processing terminal to which the transmission of a frame of data is directed, and prescribed control information, respectively,

second means for accessing the selectively addressable memory and generating a second sequence of groups of signals respectively representative of whether there is to be a change in the length of the data words, the number of data words prior to the occurrence of a word length change, and the words containing the data information, and

third means, coupled to said first and second means, for sequentially transmitting said first and second sequences of groups of signals to said at least one second processing terminal, and

at said at least one second processing terminal,

fourth means for monitoring signals transmitted by a first processing terminal and generating an output upon recognizing that the first sequence of groups of signals contains an address corresponding to said at least one second processing terminal, and

fifth means, coupled to said fourth means, for causing a frame of data read out of memory and transmitted by said first processing terminal to be disassembled and written into memory at said second processing terminal in accordance with any change in data word size as represented by said second sequence of signals;

sixth means, coupled to said first and second means, for generating a group of signals representative of a prescribed function of said first and second sequences of groups of signals and supplying said prescribed function representative group of signals to said third means for transmission subsequent to the transmission of said second sequence of groups of signals;

seventh means, coupled to said third means, for generating a pair of groups of flag signals, each of which uniquely identifies an end point of a frame of data, and supplying one of said groups of flag signals to said third means for transmission prior to the transmission of said first sequence of groups of signals and the other of said groups of flag signals to said third means for transmission subsequent to the transmission of said prescribed function representative group of signals, so that a complete frame of data transmitted by said first processing terminal to said at least one second processing terminal is comprised of a sequential arrangement of said one of said groups of flag signals, said first sequence, said second sequence, said prescribed function representative group, and the other of said groups of flag signals; and

said fourth means including means for comparing the address containing signal group with at least one receiver address code identifying said at least one second processing terminal, upon detection of said one flag signal group, to determine whether or not a frame of data transmitted from a first processing terminal is being directed to said at least one second processing terminal.

10. A data communication system according to claim 9, wherein the data information within said second sequence of groups of signals transmitted from said first processing terminal contains address code change request data and said fourth means includes means for storing at least one changeable address code identifying said second processing terminal, the address code stored in which is modified in accordance with said address code change request data, whereby, for a subsequently received frame of data, the address signal group transmitted from said first processing terminal will be compared with a new receiver address code identifying said at least one second processing terminal.

11. A data communication system according to claim 9, further comprising, at said at least one second processing terminal,

eighth means, coupled to said fourth and fifth means, for generating a group of signals representative of a preselected function of the received first and second sequences of groups of signals, and

ninth means, coupled to said eighth means and said fifth means, for comparing the prescribed function representative group of signals transmitted from said first processing terminal with said preselected function representative group of signals generated by said eighth means, whereby the correlation of the received frame with that transmitted can be determined.

12. A data communication system according to claim 9, further comprising, at said at least one second processing terminal, eighth means, coupled to said fourth means, for detecting said other of said groups of flag signals and generating an output representative of the termination of a received frame of data.

13. A data communication system for controlling the transmission and reception of a frame of data in serial format, from a first processing terminal whereat data to be transmitted is read out from a selectively addressable memory, said frame being comprised of a sequence of signals containing address, control, and data information fields, to at least one second processing terminal whereat received data is written into a selectively addressable memory, comprising:

at said first processing terminal,

first means for generating a first sequence of groups of signals containing the address of said at least one second processing terminal to which the transmission of a frame of data is directed, and prescribed control information, respectively,

second means for accessing the selectively addressable memory and generating a second sequence of groups of signals respectively representative of whether there is to be a change in the length of the data words, the number of data words prior to the occurrence of a word length change, and the words containing the data information, and

third means, coupled to said first and second means, for sequentially transmitting said first and second sequences of groups of signals to said at least one second processing terminal, and

at said at least one second processing terminal,

fourth means for monitoring signals transmitted by a first processing terminal and generating an output upon recognizing that the first sequence of groups of signals contains an address corresponding to said at least one second processing terminal, and

fifth means, coupled to said fourth means, for causing a frame of data read out of memory and transmitted by said first processing terminal to be disassembled and written into memory at said second processing terminal in accordance with any change in data word size as represented by said second sequence of signals;

sixth means, coupled to said first and second means, for generating a group of signals representative of a prescribed function of said first and second sequences of groups of signals and supplying said prescribed function representative group of signals to said third means for transmission subsequent to the transmission of said second sequence of groups of signals;

seventh means, coupled to said third means, for generating a pair of groups of flag signals, each of which uniquely identifies an end point of a frame of data, and supplying one of said groups of flag signals to said third means for transmission prior to the transmission of said first sequence of groups of signals and the other of said groups of flag signals to said third means for transmission subsequent to the transmission of said prescribed function representative group of signals, so that a complete frame of data transmitted by said first processing terminal to said at least one second processing terminal is comprised of a sequential arrangement of said one of said groups of flag signals, said first sequence, said second sequence, said prescribed function representative group, and the other of said groups of flag signals; and

eighth means, coupled to said fourth means, for monitoring the length of the frame of data and generating an invalid frame indicating signal upon recognition of said other flag signal group prior to the length of the monitored frame of data reaching a preselected value.

14. A data communication system for controlling the transmission and reception of a frame of data in serial format, from a first processing terminal whereat data to be transmitted is read out from a selectively addressable memory, said frame being comprised of a sequence of signals containing address, control, and data information fields, to at least one second processing terminal whereat received data is written into a selectively addressable memory, comprising:

at said first processing terminal,

first means for generating a first sequence of groups of signals containing the address of said at least one second processing terminal to which the transmission of a frame of data is directed, and prescribed control information, respectively,

second means for accessing the selectively addressable memory and generating a second sequence of groups of signals respectively representative of whether there is to be a change in the length of the data words, the number of data words prior to the occurrence of a word length change, and the words containing the data information, and

third means, coupled to said first and second means, for sequentially transmitting said first and second sequences of groups of signals to said at least one second processing terminal, and

at said at least one second processing terminal,

fourth means for monitoring signals transmitted by a first processing terminal and generating an output upon recognizing that the fist sequence of groups of signals contains an address corresponding to said at least one second processing terminal, and

fifth means, coupled to said fourth means, for causing a frame of data read out of memory and transmitted by said first processing terminal to be disassembled and written into memory at said second processing terminal in accordance with any change in data word size as represented by said second sequence of signals;

sixth means, coupled to said first and second means, for generating a group of signals representative of a prescribed function of said first and second sequences of groups of signals and supplying said prescribed function representative group of signals to said third means for transmission subsequent to the transmission of said second sequence of groups of signals;

seventh means, coupled to said third means, for generating a pair of groups of flag signals, each of which uniquely identifies an end point of a frame of data, and supplying one of said groups of flag signals to said third means for transmission prior to the transmission of said first sequence of groups of signals and the other of said groups of flag signals to said third means for transmission subsequent to the transmission of said prescribed function representative group of signals, so that a complete frame of data transmitted by said first processing terminal to said at least one second processing terminal is comprised of a sequential arrangement of said one of said groups of flag signals, said first sequence, said second sequence, said prescribed function representative group, and the other of said groups of flag signals;

eighth means, coupled to said third means, for selectively modifying said first and second sequences of groups of signals and said prescribed function representative group of signals so as to prevent a transmitted frame of data from containing groups of signals corresponding to said flag signals other than at those portions of a data frame where flag signals are intended to occur, and

at said at least one second processing terminal,

ninth means, coupled to said fourth means, for detecting the occurrence of any selective modification of said first and second sequences of groups of signals and said prescribed function representative groups of signals transmitted from a first processing terminal and removing said selective modification thereof so as to permit accurate disassembly of a frame of data by said fifth means.

15. A data communication system according to claim 14, further including,

at said first processing terminal,

tenth means, coupled to said third means, for generating an abort character made up of a prescribed group of signals representative of the aborting of a frame, in response to the occurrence of prescribed conditions, and supplying said abort character to said third means for immediate transmission to said at least one second processing terminal, and

at said at least one second processing terminal,

eleventh means, coupled to said fourth and fifth means, for detecting an abort character transmitted from a first processing terminal and terminating frame reception and disassembly in response thereto.

16. A data communication system according to claim 15, wherein said tenth means includes means for generating a unique group of signals as an abort character to be supplied to said third means for transmission while inhibiting the selective signal modification by said eighth means.

17. A data communication system for controlling the transmission and reception of a frame of data in serial format, from a first processing terminal whereat data to be transmitted is read out from a selectively addressable memory, said frame being comprised of a sequence of signals containing address, control, and data information fields, to at least one secoond processing terminal whereat received data is written into a selectively addressable memory, comprising:

at said first processing terminal,

first means for generating a first sequence of groups of signals containing the address of said at least one second processing terminal to which the transmission of a frame of data is directed, and prescribed control information, respectively,

second means for accessing the selectively addressable memory and generating a second sequence of groups of signals respectively representative of whether there is to be a change in the length of the data words, the number of data words prior to the occurrence of a word length change, and the words containing the data information, and

third means, coupled to said first and second means, for sequentially transmitting said first and second sequences of groups of signals to said at least one second processing terminal, and

at said at least one second processing terminal,

fourth means for monitoring signals transmitted by a first processing terminal and generating an output upon recognizing that the first sequence of groups of signals contains an address corresponding to said at least one second processing terminal, and

fifth means, coupled to said fourth means, for causing a frame of data read out of memory and transmitted by said first processing terminal to be disassembled and written into memory at said second processing terminal in accordance with any change in data word size as represented by said second sequence of signals;

sixth means, coupled to said first and second means, for generating a group of signals representative of a prescribed function of said first and second sequences of groups of signals and supplying said prescribed function representative group of signals to said third means for transmission subsequent to the transmission of said second sequence of groups of signals;

seventh means, coupled to said third means, for generating a pair of groups of flag signals, each of which uniquely identifies an end point of a frame of data, and supplying one of said groups of flag signals to said third means for transmission prior to the transmission of said first sequence of groups of signals and the other of said groups of flag signals to said third means for transmission subsequent to the transmission of said prescribed function representative group of signals, so that a complete frame of data transmitted by said first processing terminal to said at least one second processing terminal is comprised of a sequential arrangement of said one of said groups of flag signals, said first sequence, said second sequence, said prescribed function representative group, and the other of said groups of flag signals;

eighth means, coupled to said third means, for generating an abort character made up of a prescribed group of signals representative of the aborting of a frame, in response to the occurrence of prescribed conditions, and supplying said abort character to said third means for immediate transmission to said at least one second processing terminal, and

at said at least one second processing terminal,

ninth means, coupled to said fourth and fifth means, for detecting an abort character transmitted from a first processing terminal and terminating frame reception and disassembly in response thereto.

18. A method of controlling the transmission of a frame of data in serial format from a first processing terminal to at least one second processing terminal comprising the steps of:

generating and transmitting at said first processing terminal, a sequence of groups of signals containing an address code identifying said at least one second processing terminal to which a data transmission is directed, prescribed control information, and data to be received by said at least one second processing terminal, respectively; and

within the group of signals containing the data to be received by said at least one second processing terminal, selectively generating

(i) a first sequence of signals representative of whether there is to be a change in the length of the data words,

(ii) a second sequence of signals representative of the number of data words prior to the occurrence of a word length change, and

(iii) a third sequence of signals containing each of said data words;

generating and transmitting, at said first processing terminal, a first group of signals representative of a prescribed function of said sequence of groups of signals;

generating and transmitting, at said first processing terminal, a pair of groups of flag signals each of which uniquely identifies an end point of a frame of data;

so that each frame of data transmitted from said first processing terminal to said at least one second processing terminal is comprised of an initial flag signal group, a sequence of address, control, and data signal groups, a prescribed function signal group, and a terminating flag signal group;

at said first processing terminal;

selectively modifying said sequence of groups of signals and said first group of signals so as to prevent the frame of data from containing groups of signals corresponding to said flag signals other than at those portions of a data frame where flag signals are intended to occur,

generating an abort character made up of a prescribed group of signals representative of the aborting of a frame, in response to the occurrence of prescribed conditions, and transmitting said abort character to said at least one second processing terminal.

19. A method according to claim 18, wherein the generation and transmission of an abort character at a first processing terminal comprises the generation and transmission of a unique group of signals as an abort character while inhibiting the selective modification of said sequence of groups of signals and said first group of signals.

20. A data communication system for controlling the transmission of a frame of data in serial format from a first processing terminal to at least one second processing terminal, said frame being comprised of a sequence of signals containing address, control, and data information fields, comprising:

at said first processing terminal,

first means for generating a first sequence of groups of signals containing the address of said at least one second processing terminal to which the transmission of a frame of data is directed, and prescribed control information, respectively,

second means for accessing the selectively addressable memory and generating a second sequence of groups of signals respectively representative of whether there is to be a change in the length of the data words, the number of data words prior to the occurrence of a word length change, and the words containing the data information;

third means, coupled to said first and second means, for sequentially transmitting said first and second sequence of groups of signals to said at least one second processing terminal;

fourth means, coupled to said first and second means, for generating a group of signals representative of a prescribed function of said first and second sequences of groups of signals and supplying said prescribed function representative group of signals to said third means for transmission subsequent to the transmission of said second sequence of groups of signals;

fifth means, coupled to said third means, for generating a pair of groups of flag signals, each of which uniquely identifies an end point of a frame of data, and supplying one of said groups of flag signals to said third means for transmission prior to the transmission of said first sequence of groups of signals and the other of said groups of flag signals to said third means for transmission;

sixth means, coupled to said third means, for selectively modifying said first and second sequences of groups of signals and said prescribed function representative group of signals so as to prevent a transmitted frame of data from containing groups of signals corresponding to said flag signals other than at those portions of a data frame where flag signals are intended to occur; and

seventh means, coupled to said third means, for generating an abort character made up of a prescribed group of signals representative of the aborting of a frame, in response to the occurrence of prescribed conditions, and supplying said abort character to said third means for immediate transmission to said at least one second processing terminal.

21. A data communication system according to claim 20, wherein said seventh means includes means for generating a unique group of signals as an abort character to be supplied to said third means for transmission while inhibiting the selective signal modification by said eighth means.