Data communication method using identification protocol

• US 5,627,544 A
• Filed: 03/18/1996
• Issued: 05/06/1997
• Est. Priority Date: 12/15/1992
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Tuttle, John R., Rotzoll, Robert R., Allen, David H., Snodgrass, Charles K., Pax, George E.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/619,274
• Time in Patent Office: 414 Days
• Field of Search: 342/42, 342/44, 342/50, 342/51
• US Class Current: 342/42
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/78 discriminating between different kinds of targets, e.g. IFF-radar, i.e. identification of friend or foe G01S13/75, G01S13/79 take precedence
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/073 Special arrangements for circuits, e.g. for protecting identification code in memory protection against unauthorised use of computer memory G06F12/14
• CPC Class Codes: G06K 7/10019 resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. collision between the communication channels used by wireless communication devices, where the solution is not particularly adapted for RFIDs or the like, H04W74/08
• CPC Class Codes: H04L 2101/604 Address structures or formats
• CPC Class Codes: H04L 2101/622 Layer-2 addresses, e.g. medium access control [MAC] addresses
• CPC Class Codes: H04L 61/35 involving non-standard use of addresses for implementing network functionalities, e.g. coding subscription information within the address or functional addressing, i.e. assigning an address to a function
• CPC Class Codes: H04L 61/5038 for local use, e.g. in LAN or USB networks, or in a controller area network [CAN]
• CPC Class Codes: H04L 61/5046 Resolving address allocation conflicts; Testing of addresses testing when self-assigning an address H04L61/5092
• CPC Class Codes: H04L 61/5069 for group communication, multicast communication or broadcast communication
• CPC Class Codes: H04L 61/5084 Providing for device mobility network addressing or numbering for mobility support in wireless networks H04W8/26; mobile IP H04W80/04
• CPC Class Codes: H04L 61/5092 by self-assignment, e.g. picking addresses at random and testing if they are already in use

Abstract

A protocol is used to coordinate the use of a common communication medium by one or more interrogating commander stations and an unknown plurality of responding responder stations. Each commander station and each responder station is equipped to broadcast messages and to check for error in received messages. When more than one station attempts to broadcast simultaneously, an erroneous message is received and communication is interrupted. To establish uninterrupted communication, a commander station broadcasts a command causing each responder station of a potentially large first number of responder stations to each select a random number from a known range and retain it as its arbitration number. After receipt of such a command, each addressed responder station transmits a response message containing its arbitration number. Zero, one, or several responses may occur simultaneously. By broadcasting requests for identification to various subsets of the full range of arbitration numbers and checking for an immediate error-free response, a commander station can determine the arbitration number of every responder station capable of communicating at the time. Consequently, a commander station can conduct subsequent uninterrupted communication with each responder station, for example by addressing only one responder station. Responder stations of this invention require minimal logic and circuitry to respond to multiple commander stations.

Claims

1. A method for one of a plurality of responder transceivers to respond to interrogation messages from two or more commander transceivers, wherein the responder is characterized by an address, and wherein each of the interrogation messages specifies a set of one or more addresses for response, comprising the steps of:

(a) upon receiving a first interrogation message from a first one of the commander transceivers, said one responder transceiver determining whether the first interrogation message specifies for response a set of one or more addresses which includes the responder'"'"'s address, and

(1) if so, then said responder transceiver transmitting a response message to the first commander transceiver, otherwise

(2) if not, then said responder transceiver initiating a waiting period of time during which the responder will not transmit a response message to any subsequent interrogation message which the responder may receive from any other one of the commander transceivers, wherein the waiting period is great enough that any response message transmitted by the responder after the waiting period would not collide with any response message transmitted by any other one of the responder transceivers in response to said first interrogation message; and

(b) upon receiving a second interrogation message from a second one of the commander transceivers, said one responder transceiver transmitting a response message to the second commander transceiver if the waiting period has expired and the second interrogation message specifies for response a set of one or more addresses which include the responder'"'"'s address;

(c) whereby any response message transmitted by said one responder transceiver to a second commander transceiver will not collide with any response message transmitted by another responder transceiver in response to the first interrogation message, thereby avoiding any false indication that two responder transceivers both have addresses belonging to said set of one or more addresses specified for response in the first interrogation message.

2. A method of addressing messages from a commander transceiver to a selected one or more of a number of responder transceivers, comprising the steps of:

(A) establishing a first predetermined number of bits to be used for unique identification numbers, and establishing for each responder transceiver a unique identification number having said predetermined number of bits;

(B) establishing a second predetermined number of bits to be used for arbitration addresses, the second number being less than the first number, and establishing a set of possible arbitration addresses having said second number of bits;

(C) the commander transceiver transmitting a first Generate command message requesting responder transceivers which receive the first Generate command message to select a new arbitration address;

(D) the commander transceiver transmitting an Identify command message requesting responder transceivers having arbitration addresses within a specified group of arbitration addresses to respond identifying themselves, said specified group being less than or equal to the entire set of possible arbitration addresses; and

(E) after receiving the first Generate command message, each responder transceiver choosing an arbitration address from the set of possible arbitration addresses, wherein each responder transceiver chooses its arbitration address independently of arbitration addresses chosen by all other responder transceivers; and

(F) after receiving the Identify command message, each responder transceiver

(1) determining whether its chosen arbitration address is within the group specified in the Identify command message, and, only if it is, then

(2) transmitting an Arbitration ID message containing its chosen arbitration address and transmitting a Unique ID message containing its unique identification number.

3. A method according to claim 2, wherein the Arbitration ID message and the Unique ID message transmitted by each responder transceiver are combined as a single message transmitted by said transponder.

4. A method according to claim 2, further comprising the subsequent steps of:

in response to receiving Arbitration ID messages from different responder transceivers containing the same arbitration address, the commander transceiver transmitting a second Generate command message; and

in response to receiving the second Generate command message, each responder transceiver choosing an arbitration address from the set of possible arbitration addresses to replace its previously chosen arbitration address, wherein each responder transceiver chooses its arbitration address independently of any arbitration addresses chosen by other responder transceivers.

5. A method according to claim 2, further comprising the subsequent steps of:

in response to receiving Arbitration ID messages from different responder transceivers containing the same chosen arbitration address, the commander transceiver transmitting a second Generate command message addressed to a specified group of arbitration addresses, wherein the group specified in the second Generate message includes said same chosen arbitration address and is less than or equal to the entire set of possible arbitration addresses; and

each responder transceiver which receives the second Generate command message;

(i) determining whether its most recently chosen arbitration address is within the group of arbitration addresses specified in the second Generate command message, and, only if so, then

(ii) choosing an arbitration address from the set of possible arbitration addresses to replace its previously chosen arbitration address, wherein said responder transceiver chooses its arbitration address independently of any arbitration addresses chosen by other responder transceivers.

6. A method according to claim 2, wherein

in response to receiving an undamaged Arbitration ID message containing the arbitration address of a responder transceiver, the commander transceiver transmitting a command message individually addressed to that responder transceiver;

and

the step of each responder transceiver transmitting the Unique ID message is delayed until the responder transceiver receives said individually addressed command message from the commander transceiver.

7. A method according to claim 2, further comprising the steps of:

providing in each responder transceiver a memory device which includes a Response Lock flag having a clear state and a set state;

the commander transceiver, before transmitting an Identify command message for the first time, transmitting a Clear Response Lock command message;

each responder transceiver, upon receiving from the commander transceiver a Clear Response Lock command message, clearing the Response Lock flag within the transceiver;

after receiving an undamaged Arbitration ID message containing the arbitration address of a responder transceiver, the commander transceiver transmitting a Set Response Lock command message addressed to that responder transceiver;

each responder transceiver, upon receiving from the commander transceiver a Set Response Lock command message addressed to said responder transceiver, setting the Response Lock flag within the transceiver; and

each responder transceiver, after receiving an Identify command message;

(i) determining whether the Response Lock flag within said responder transceiver is set, and, if so, then

(ii) not performing said step of transmitting an Arbitration ID message and a Unique ID message, irrespective of whether the arbitration address of said responder transceiver is within the group specified in the Identify command message.

8. A method according to claim 2, further comprising the steps of:

providing in each responder transceiver a memory device which includes a Response Lock flag having a clear state and a set state;

the commander transceiver, before transmitting an Identify command message for the first time, transmitting a Clear Response Lock command message;

each responder transceiver, upon receiving from the commander transceiver a Clear Response Lock command message, clearing the Response Lock flag within the transceiver;

after receiving an undamaged Arbitration 1D message containing the arbitration address of a responder transceiver, the commander transceiver transmitting a Set Response Lock command message addressed to that responder transceiver;

each responder transceiver, upon receiving from the commander transceiver a Set Response Lock command message addressed to said responder transceiver, setting the Response Lock flag within the transceiver;

in response to receiving Arbitration ID messages from different responder transceivers containing the same arbitration address, the commander transceiver transmitting a second Generate command message; and

in response to receiving the second Generate command message, each responder transceiver;

(i) determining whether the Response Lock flag within said responder transceiver is clear and, only if so, then

(ii) choosing an arbitration address for said responder transceiver from the set of possible arbitration addresses to replace its previously chosen arbitration address, wherein each responder transceiver chooses its arbitration address independently of any arbitration addresses chosen by other responder transceivers.

9. For use with a number of responder transceivers, each of which is characterized by an address, a method for a commander transceiver to interrogate the responder transceivers to determine their addresses, comprising the steps of:

(A) providing in each responder transceiver a memory device which includes a Response Lock flag having a clear state and a set state;

(B) the commander transceiver transmitting a Clear Response Lock command message;

(C) each responder transceiver which receives the Clear Response Lock command message clearing the Response Lock flag within said responder transceiver;

(D) the commander transceiver transmitting a number of Identify command messages, wherein each Identify command message requests each responder transceiver having an address within a specified group of addresses to identify itself, and wherein each respective group specified in each respective Identify command message is less than or equal to the entire set of possible addresses;

(E) each responder transceiver which receives an Identify command message;

(1) determining whether the address of said responder transceiver is within the subset specified in the received Identify command message and determining whether said responder'"'"'s Response Lock flag is clear, and, only if both determinations are true, then

(2) transmitting an ID Response message containing the address of said responder transceiver;

(F) the commander transceiver;

(1) determining whether it receives an undamaged ID Response message from a responder transceiver, and, if so, then

(2) transmitting a Set Response Lock command message addressed to the responder transceiver from which the commander transceiver received the uncorrupted ID Response message; and

(G) each responder transceiver which receives a Set Response Lock command message addressed to that responder transceiver;

setting the Response Lock flag within that responder transceiver.

10. A method for a commander transceiver to interrogate a number of responder transceivers to determine their addresses, comprising the steps of:

(A) establishing a set of possible addresses for the responder transceivers;

(B) the commander transceiver transmitting a first Generate command message requesting responder transceivers having addresses within a specified group of addresses to generate new addresses, the specified group being less than or equal to the entire set of possible addresses;

(C) each responder transceiver which receives the first Generate command message;

only if the address of said responder transceiver is within the group specified in the first Generate command message, assigning to itself an address within said set of possible addresses;

(D) the commander transceiver transmitting an Identify command message requesting responder transceivers having addresses within a specified group of addresses to identify themselves, wherein the group specified in the Identify command message is less than or equal to the entire set of possible addresses;

(E) each responder transceiver which receives an Identify command message;

only if the address of said responder transceiver is within the group specified in the received Identify command message, transmitting an ID Response message containing the address of said responder transceiver;

(F) in response to receiving ID Response messages from a plurality of responder transceivers, the commander transceiver;

(1) determining whether the ID Response messages sent by the responder transceivers indicate a likelihood that any one of the addresses was assigned to two or more different responder transceivers, and, if so, then

(2) transmitting a second Generate command message requesting responder transceivers having addresses within a specified group of addresses to generate new addresses, the specified group being less than or equal to the entire set of possible addresses;

(G) each responder transceiver which receives the second Generate command message;

only if the address of said responder transceiver is within the group specified in the second Generate command message, assigning to itself an address within said set of possible addresses; and

(H) returning to Step (D) of the commander transceiver transmitting an Identify command message.

11. An interrogation method according to claim 10, wherein:

said Step (C) of assigning itself an address further comprises said responder transceiver choosing its address from the set of possible addresses independently of other responder transceivers'"'"' choosing their respective addresses; and

said Step (G) of assigning itself an address further comprises said responder transceiver choosing its address from the set of possible addresses independently of other responder transceivers'"'"' choosing their respective addresses.

12. An interrogation method according to claim 10, wherein Step (F)(1) of the commander transceiver determining whether any one of the addresses was assigned to two or more different responder transceivers further comprises the sub-steps of:

repeating Steps (D) and (E) using different specified groups of addresses in successive repetitions of Step (D); and

after each repetition of Step (E), the commander transceiver determining that none of the individual addresses within the group specified in the Identify command message transmitted in the preceding Step (D) was assigned to two or more different responder transceivers if the commander transceiver receives an ID Response message from either zero or one responder transceiver during said Step (E).

13. An interrogation method according to claim 10, further comprising the step of:

in response to the commander transceiver receiving an undamaged ID Response message from a responder transceiver, the commander transceiver transmitting a Data Transfer command message individually addressed to said responder transceiver.

14. An interrogation method according to claim 13, further comprising the step of:

after the commander transceiver transmits a Data Transfer command message individually addressed to a responder transceiver, said responder transceiver transmitting to the commander transceiver a message containing data acquired by said responder transceiver.

15. An interrogation method according to claim 10, further comprising the steps of:

in response to the commander transceiver receiving an undamaged ID Response message from a responder transceiver, the commander transceiver transmitting a Set Response Lock command message individually addressed to said responder transceiver; and

if said one responder transceiver receives the Set Response Lock command message, said responder setting a Response Lock flag in a memory device within said responder transceiver.

16. An interrogation method according to claim 15, wherein Step (G) further comprises the sub-steps of:

before assigning to itself an address, each responder transceiver determining whether its Response Lock flag is set, and, if so, then

not performing the step of assigning to itself an address in Step (G), irrespective of whether its address is within the group specified in the second Generate command message, whereby the responder transceiver retains its previously assigned address.

17. An interrogation method according to claim 10, wherein the group specified in the second Generate command message is the same as the group specified in the first Generate command message.

18. An interrogation method according to claim 10, wherein the group specified in the second Generate command message includes each of said addresses which was determined by the commander transceiver in Step (F)(1) as having a likelihood of belonging to at least two responder transceivers.

19. A method for a commander transceiver to interrogate a number of responder transceivers to determine their addresses, comprising the steps of:

(A) providing in each responder transceiver a memory device which includes a Response Lock flag having a clear state and a set state;

(B) establishing a set of possible addresses for the responder transceivers;

(C) the commander transceiver transmitting a Clear and Generate command message;

(D) each responder transceiver which receives the Clear and Generate command message;

(1) clearing the Response Lock flag within said responder transceiver,

(2) assigning to itself an address chosen from said set of possible addresses, and

(3) transmitting an ID Response message containing the address of said responder transceiver;

(E) the commander transceiver transmitting a Set Response Lock command message addressed to each responder transceiver from which the commander transceiver receives an uncorrupted ID Response message;

(F) each responder transceiver, upon receipt of a Set Response Lock command message addressed to that responder transceiver, setting the Response Lock flag within that responder transceiver;

(G) the commander transceiver;

(1) determining whether the ID Response messages sent by the responder transceivers indicate a likelihood that any one of the addresses was assigned to two or more different responder transceivers, and, if so, then

(2) transmitting a Generate command message;

(H) each responder transceiver which receives the Generate command message;

(1) determining whether the Response Lock flag within that responder transceiver is clear, and, if so, then

(2) assigning to itself an address chosen from said set of possible addresses, and transmitting an ID Response message containing the address of said responder transceiver; and

(I) returning to Step (E) of the commander transceiver transmitting a Set Response Lock command message.

20. A method according to claim 19, further comprising the steps of:

after transmitting the Clear and Generate command message, the commander transceiver transmitting a first Identify command message requesting responder transceivers having addresses within a specified group of addresses to identify themselves, wherein the group specified in the first Identify command message is less than or equal to the entire set of possible addresses; and

after transmitting the Generate command message, the commander transceiver transmitting a second Identify command message requesting responder transceivers having addresses within a specified group of addresses to identify themselves, wherein the group specified in the second Identify command message is less than or equal to the entire set of possible addresses;

wherein each responder transceiver delays transmitting an ID Response message until it receives from the commander transceiver an Identify command message specifying a group of addresses which includes the address of said responder transceiver.

21. A method according to claim 20, wherein Step (G)(1) of the commander transceiver determining whether the ID Response messages indicate a likelihood of one address being assigned to different responders further comprises the sub-step of:

after each transmission of an Identify command message, the commander transceiver determining that none of the individual addresses within the group specified in said Identify message was assigned to different responder transceivers if the commander transceiver receives an ID Response message from either zero or one responder transceiver in response to said Identify command message.

22. A method according to claim 20, wherein the commander transceiver transmits the Clear and Generate command message in Step (C) concurrently with transmitting the first Identify command message, wherein the Clear and Generate command message and the first Identify command message are combined in a single transmitted message.

23. A method according to claim 20, wherein:

(a) said Step (D)(2) of assigning to itself an address further comprises said responder transceiver choosing its address independently of other responder transceivers'"'"' choosing their respective addresses; and

(b) said Step (H)(2) of assigning to itself an address further comprises said responder transceiver choosing its address independently of other responder transceivers'"'"' choosing their respective addresses.

24. An interrogation method according to claim 20, wherein said Step (D)(3) performed by each responder transceiver further comprises the sub-steps of:

(a) before performing the sub-step of transmitting said ID Response message, determining whether the Response Lock flag within said responder transceiver is set, and, if so, then

(b) not performing the sub-step of transmitting said ID Response message, irrespective of whether the address of said responder transceiver is within the group specified in a received Identify command message.

25. An interrogation method according to claim 19, wherein said Step (D)(3) performed by each responder transceiver further comprises the sub-steps of:

(a) before performing the sub-step of transmitting said ID Response message, determining whether the Response Lock flag within said responder transceiver is set, and, if so, then

(b) not performing the sub-step of transmitting said ID Response message.

26. An interrogation method according to claim 19, wherein said Step (F) of each responder transceiver setting its Response Lock flag upon receipt of a Set Response Lock command message further includes the sub-step of:

said responder transceiver transmitting to the commander transceiver a message containing data acquired by the responder transceiver.

27. A method for a commander transceiver to interrogate a number of responder transceivers to determine their addresses, comprising the steps of:

(A) providing in each responder transceiver a memory device which includes a Response Lock flag having a clear state and a set state;

(B) establishing a set of possible addresses for the responder transceivers;

(C) the commander transceiver transmitting a Clear and Generate command message;

(D) each responder transceiver which receives the Clear and Generate command message;

(1) clearing a Response Lock flag in a memory device within that responder transceiver, and

(2) assigning to itself an address by choosing its address from said set of possible addresses independently of other responder transceivers'"'"' choosing their respective addresses;

(E) the commander transceiver selecting a subset of addresses which is less than or equal to the entire set of possible addresses;

(F) the commander transceiver transmitting an Identify command message requesting responder transceivers having addresses within a specified subset of addresses to identify themselves, wherein the subset specified in the Identify command message is the subset last selected by the commander transceiver;

(G) each responder transceiver which receives an Identify command message;

(1) determining whether the address of said responder transceiver is within the subset specified in the received Identify command message, and, only if true, then

(2) transmitting an ID Response message containing the address of said responder transceiver;

(H) the commander transceiver;

(1) determining whether it receives an ID Response message from a responder transceiver which is not corrupted by a collision with another message, and, if so, then

(2) transmitting a Set Response Lock command message addressed to the responder transceiver from which the commander transceiver received the uncorrupted ID Response message;

(I) each responder transceiver, upon receipt of a Set Response Lock command message addressed to that responder transceiver, setting the Response Lock flag within that responder transceiver;

(J) the commander transceiver determining whether the previously transmitted Identify command messages specified every subset which could contain a unique responder transceiver, and

(1) if so, then performing Step (M), otherwise

(2) if not, then performing Step (K);

(K) the commander transceiver selecting a subset of addresses, the selected subset being less than or equal to the entire set of possible addresses;

(L) returning to Step (F) of the commander transceiver transmitting a Identify command message;

(M) the commander transceiver;

(1) determining whether the commander transceiver previously received colliding messages in response to a previously transmitted Identify command message which specified a subset containing only a single responder address, and, if so, then

(2) transmitting a Generate command message;

(N) each responder transceiver which receives the Generate command message;

(1) determining whether the Response Lock flag within that responder transceiver is clear, and, if so, then

(2) assigning to itself an address by choosing its address from said set of possible addresses independently of other responder transceivers'"'"' choosing their respective addresses; and

(O) returning to Step (E) of the commander transceiver selecting a subset of addresses.

28. An interrogation method according to claim 27, wherein said Step (K) of the commander transceiver selecting a subset of addresses further comprises the selected subset being different from the subset specified in the Identify command message last transmitted by the commander transceiver.

29. An interrogation method according to claim 27, wherein said Step (G) performed by each responder transceiver further comprises the sub-steps of:

(a) before performing Sub-Step (G)(2) of transmitting said ID Response message, determining whether the Response Lock flag within said responder transceiver is set, and, if so, then

(b) not performing Sub-Step (G)(2) of transmitting said ID Response message, irrespective of the address determination in Sub-Step (G)(1).

30. An interrogation method according to claim 27, wherein said Step (I) of each responder transceiver setting its Response Lock flag upon receipt of a Set Response Lock command message further includes the sub-step of:

said responder transceiver transmitting to the commander transceiver a message containing data acquired by the responder transceiver.

31. An interrogation method according to claim 27, wherein the commander transceiver transmits the Clear and Generate command message in Step (C) concurrently with transmitting the Identify command message in the first performance of Step (F), wherein the Clear and Generate command message and the Identify command message are combined in a single transmitted message.

32. A method for a responder communications transceiver to identify itself in response to messages received from a commander communications transceiver, comprising the steps of:

establishing a set of possible responder arbitration addresses; and

in response to receiving a first Generate command message from a commander transceiver, said responder transceiver assigning to itself an arbitration address by randomly choosing a first address from the set of possible responder arbitration addresses;

wherein said responder transceiver chooses its arbitration address independently of arbitration addresses chosen by any other responder transceiver.

33. A method according to claim 32, wherein the responder transceiver performs the step of choosing its arbitration address only if the arbitration address of the responder currently is within a group of addresses specified in the first Generate command message.

34. A method according to claim 32, further comprising the step of:

in response to receiving a second Generate command message from the commander transceiver, said responder transceiver randomly choosing a second address from the set of possible responder addresses and assigning to itself as its arbitration address the second address in place of the first address.

35. A method according to claim 34, wherein the responder transceiver performs the step of choosing a second address as its arbitration address only if the arbitration address of the responder currently is within a group of addresses specified in the second Generate command message.

36. A method according to claim 32, further comprising the step of:

after the step of choosing its arbitration address, the responder transceiver transmitting an Arbitration ID message containing its chosen arbitration address.

37. A method according to claim 36, wherein the responder transceiver performs the step of transmitting an Arbitration ID message only after the responder transceiver receives from the commander transceiver an Identify command message which specifies for response a group of addresses which includes the arbitration address of the responder transceiver.

38. A method according to claim 36, further comprising the step of:

in response to receiving from the commander transceiver a message individually addressed to said responder, setting a Response Lock flag in a memory device within the responder transceiver.

39. A method according to claim 38, wherein the step of setting the Response Lock flag further comprises said responder transceiver transmitting to the commander transceiver a message containing data stored in a data memory device within the responder transceiver.

40. A method according to claim 38, further comprising the step of:

in response to receiving a second Generate command message from the commander transceiver, and only if said responder'"'"'s Response Lock flag is not set, said responder transceiver choosing a second random address from the set of possible responder addresses and assigning to itself as its arbitration address the second random address in place of the first random address.

41. A method according to claim 38, further comprising the step of:

in response to receiving from the commander transceiver an Identify command message which specifies for response a group of addresses which includes the arbitration address of the responder transceiver, and only if said responder'"'"'s Response Lock flag is not set, said responder transceiver transmitting an Arbitration ID message containing its chosen arbitration address.

42. A method according to claim 36, further comprising the step of:

in response to receiving from the commander transceiver a Set Response Lock command message addressed to said responder transceiver, said responder transceiver setting a Response Lock flag in a memory device within the responder transceiver.

43. A method according to claim 42, wherein the step of setting the Response Lock flag further comprises said responder transceiver transmitting to the commander transceiver a message containing data stored in a data memory device within the responder transceiver.

44. A method according to claim 42, further comprising the step of:

in response to receiving a second Generate command message from the commander transceiver, and only if said responder'"'"'s Response Lock flag is not set, said responder transceiver choosing a second random address from the set of possible responder addresses and assigning to itself as its arbitration address the second random address in place of the first random address.

45. A method according to claim 42, further comprising the step of:

in response to receiving from the commander transceiver an Identify command message which specifies for response a group of addresses which includes the arbitration address of the responder transceiver, and only if said responder'"'"'s Response Lock flag is not set, said responder transceiver transmitting an Arbitration ID message containing its chosen arbitration address.

46. A method for a responder transceiver to identify itself in response to messages received from a commander transceiver, comprising the steps of:

(a) establishing for said responder transceiver a unique identification number having a first number of bits;

(b) establishing a set of possible arbitration addresses, wherein each arbitration address has a second number of bits, the second number being less than the first number;

(c) in response to receiving a first Generate command message from a commander transceiver, said responder transceiver assigning to itself an arbitration address by randomly choosing a first address from said set of possible responder arbitration addresses, wherein said responder transceiver chooses its arbitration address independently of arbitration addresses chosen by any other responder transceiver; and

(d) in response to receiving from the commander transceiver an Identify command message which specifies for response a group of addresses which includes the arbitration address of the responder transceiver;

(i) said responder transceiver transmitting an Arbitration ID message containing its chosen arbitration address, and

(ii) said responder transceiver transmitting a Unique ID message containing its unique identification number.

48. A method according to claim 46, wherein the Arbitration ID message and the Unique ID message are combined as a single transmitted message.

49. A method according to claim 46, further comprising the steps of:

in response to receiving a second Generate command message from the commander transceiver, said responder transceiver choosing a second random address from the set of possible responder addresses and assigning to itself as its arbitration address the second random address in place of the first random address.

50. A method according to claim 49, wherein the responder transceiver performs the step of choosing a second random address and assigning the second address as its arbitration address only if the arbitration address of the responder currently is within a group of addresses specified in the second Generate command message.

51. A method according to claim 46, further comprising the step of:

in response to receiving from the commander transceiver a message individually addressed to said responder'"'"'s arbitration address, setting a Response Lock flag in a memory device within the responder transceiver.

52. A method according to claim 51, further comprising the step of:

in response to receiving a second Generate command message from the commander transceiver, and only if said responder'"'"'s Response Lock flag is not set, said responder transceiver choosing a second random address from the set of possible responder addresses and assigning to itself as its arbitration address the second random address in place of the first random address.

53. A method according to claim 51, wherein said responder transceiver performs the step of transmitting an Arbitration ID message only if said responder'"'"'s Response Lock flag is not set.

47. A method according to claim 69, wherein the step of said responder transceiver transmitting the Unique ID message is delayed until the responder transceiver receives from the commander transceiver a message individually addressed to said responder'"'"'s arbitration address.