Message recipient discrimination using start-of-packet delimiters

Abstract

Methods and apparatus for operating a communication system comprising three or more communication transceivers. In illustrative embodiments, multiple unique start-of-packet delimiters are maintained. A data packet to be transmitted is constructed using a specified one of the plurality of start-of-packet delimiters to demarcate the start of said data packet. The chosen start-of-packet delimiter reflects one or more transceivers that are intended recipients of said data packet. When a data packet is received by a transceiver, the start-of-packet delimiter of the received data packet is compared to one or more valid start-of-packet delimiters for the receiving transceiver. If the start-of-packet delimiter of the received data packet matches a valid start-of-packet delimiter for the receiving transceiver, the data packet is accepted, otherwise it is rejected.

What is claimed is: 
     
       1. A method of operating a transceiver in a communication system, the method comprising:
 maintaining a plurality of unique start-of-packet delimiters; 
 constructing a data packet to be transmitted using a specified one of the plurality of start-of-packet delimiters to demarcate the start of said data packet, the chosen start-of-packet delimiter reflecting one or more transceivers that are intended recipients of said data packet; and 
 when receiving a data packet is received, by a the transceiver:, the data packet including a start-of-packet (SOP) delimiter to demarcate the start of the data packet, the SOP delimiter including code words; 
 comparing, by the transceiver, the start-of-packet code words of the SOP delimiter of the received data packet to one or more valid start-of-packet delimiters for the receiving transceiver corresponding code words of a stored SOP delimiter; and 
 if the start-of-packet delimiter ofrejecting, by the transceiver, the received data packet matches a valid start-of-packetwhen the code words of the received SOP delimiter do not match code words of the stored SOP delimiter for the receiving transceiver, accepting said data packet, otherwise rejecting said data packet; 
 wherein the communication system is a universal serial bus (USB) communication system and wherein said transceivers comprise the transceiver comprises a USB power-delivery (USB-PD) transceivers transceiver. 
 
     
     
       2. The method of  claim 1  wherein the communication system comprises a first transceiver, a second transceiver, and a third transceiver, and wherein the plurality of unique start-of-packet delimiters comprises a first start-of-packet delimiter and a second start-of-packet delimiter, wherein the first and second transceivers are capable of both sending and receiving data packets having either the first start-of-frame delimiter or the second start-of-frame delimiter, and wherein the third transceiver is capable of sending and receiving data packets having only the second start-of-packet delimiter:
 the code words of the received SOP delimiter includes first, second, third, and fourth code words; 
 the code words of the stored SOP delimiter includes first, second, third, and fourth code words corresponding to the first, second, third, and fourth code words of the received SOP delimiter; and 
 the step of rejecting includes the first code word of the received SOP delimiter is different from the first code word of the stored SOP delimiter. 
 
     
     
       3. The method of claim  2  1, wherein the first transceiver resides in a first USB-capable device and the second transceiver resides in a second USB-capable device, and wherein the third transceiver resides in a USB cable plug of a USB cable:
 the code words of the received SOP delimiter includes first, second, third, and fourth code words; 
 the code words of the stored SOP delimiter includes first, second, third, and fourth code words corresponding to the first, second, third, and fourth code words of the received SOP delimiter; and 
 the step of rejecting includes the second code word of the received SOP delimiter is different from the second code word of the stored SOP delimiter. 
 
     
     
       4. The method of claim  3  1, wherein the bit sequence of said first start-of-packet delimiter is 00011000110001110001 and the bit sequence of said second start-of-packet delimiter is 00011001110110001100:
 the code words of the received SOP delimiter includes first, second, third, and fourth code words; 
 the code words of the stored SOP delimiter includes first, second, third, and fourth code words corresponding to the first, second, third, and fourth code words of the received SOP delimiter; and 
 the step of rejecting includes the third code word of the received SOP delimiter is different from the third code word of the stored SOP delimiter. 
 
     
     
       5. The method of claim  4  1, wherein the communication system further comprises a fourth transceiver residing in a second USB cable plug of said USB cable, and wherein the plurality of unique start-of-packet delimiters further comprises a third start-of-packet delimiter, and wherein the first and second transceivers are capable of both sending and receiving data packets having the third start-of-frame delimiter, and wherein the fourth transceiver is capable of sending and receiving data packets having only the third start-of-packet delimiter:
 the code words of the received SOP delimiter includes first, second, third, and fourth code words; 
 the code words of the stored SOP delimiter includes first, second, third, and fourth code words corresponding to the first, second, third, and fourth code words of the received SOP delimiter; and 
 the step of rejecting includes the fourth code word of the received SOP delimiter is different from the fourth code word of the stored SOP delimiter. 
 
     
     
       6. The method of claim  5  1, wherein the bit sequence of said third start-of-packet delimiter is 00011011000001101100:
 the code words of the received SOP delimiter includes a first sequence of 20 bits; 
 the code words of the stored SOP delimiter includes second sequence of 20 bits corresponding to the first sequence of 20 bits of the received SOP delimiter; and 
 the step of rejecting includes one or more bits in the first sequence of 20 bits of the received SOP delimiter is different from the corresponding one or more bits in the second sequence of 20 bits of the stored SOP delimiter. 
 
     
     
       7. The method of claim  1  6, further comprising:
 maintaining a hard-reset code operable to cause a hard reset of any transceiver that receives saidcomparing, by the transceiver, the SOP delimiter of the received data packet to a stored hard-reset code; and 
 if a hard reset of the transceivers in the communication system is desired, transmitting a communication having the hard-reset code in the start-of-packet delimiter portion of the transmitted data in place of a start-of-packet delimiter; and 
 when a communication is received by a transceiver:
 comparing the start-of-packet delimiter portion of the transmitted data to the hard-reset code; and 
 if the start-of-packet delimiter portion of the transmitted data matches the hard-reset code, 
 
 performing a hard reset of, by a controller coupled to the receiving transceiver, when and only when the SOP delimiter of the received data packet is a complete match with the stored hard-reset code. 
 
     
     
       8. The method of  claim 7 , wherein the communication system comprises a first transceiver, a second transceiver and a third transceiver, and wherein the method further comprises:
 maintaining a second hard-reset code operable to cause a reset of the third transceiver without causing a hard reset of the first and second transceivers; 
 if a hard reset of the third transceiver but not the first and second transceivers is desired, transmitting a communication having the second hard-reset code in the start-of-packet delimiter portion of the transmitted data in place of a start-of-packet delimiter; and 
 when a communication is received by the third transceiver:
 comparing the start-of-packet delimiter portion of the transmitted data to the second hard-reset code; and 
 if the start-of-packet delimiter portion of the transmitted data matches said second hard-reset code, performing a hard reset of the third transceiver: 
 
 the received SOP delimiter includes a first sequence of 20 bits; 
 the stored hard-reset code includes second sequence of 20 bits corresponding to the first sequence of 20 bits of the received SOP delimiter; and 
 the complete match includes the first sequence of 20 bits of the received SOP delimiter having same values as the second sequence of 20 bits of the stored hard-reset code. 
 
     
     
       9. The method of claim  8  1, wherein the first transceiver resides in either a first USB-capable device and the second transceiver resides in a second USB-capable device, and wherein the third transceiver resides in or a USB cable plug of a USB cable. 
     
     
       10. A method of operating a data transmitter to indicate an intended one or more recipients of a data packet to be transmitted, the method comprising:
 maintaining a plurality of unique start-of-packet delimiters, each start-of-packet delimiter being associated with one or more transceivers that are potential communication partners; 
 determining one or more transceivers that are intended recipients of a data packet to be transmitted; 
 selecting one of said plurality of start-of-packet delimiters based on which one or more transceivers are intended recipients of said data packet; and 
 constructing said data packet using the selected start-of-packet delimiter to demarcate the start of said data packet; 
 wherein said data transmitter comprises a universal serial bus power-delivery (USB-PD) transmitter and wherein said one or more transceivers comprise USB-PD transceivers. 
 
     
     
       11. A method of operating a data transmitter to indicate an intended one or more recipients of a data packet to be transmitted, the method comprising:
 maintaining a plurality of unique start-of-packet delimiters, each start-of-packet delimiter being associated with one or more transceivers that are potential communication partners; 
 determining one or more transceivers that are intended recipients of a data packet to be transmitted; 
 selecting one of said plurality of start-of-packet delimiters based on which one or more transceivers are intended recipients of said data packet; and 
 constructing said data packet using the selected start-of-packet delimiter to demarcate the start of said data packet; 
 wherein said data transmitter is operable to communicate with a second transceiver and a third transceiver, wherein said plurality of unique start-of-packet delimiters comprises a first start-of-packet delimiter and a second start-of-packet delimiter, and wherein said selecting one of said plurality of start-of-packet delimiters comprises selecting the first start-of-packet delimiter if the second transceiver is the only intended recipient of the data packet and selecting the second start-of-packet delimiter if both the second and third transceivers are intended recipients of the data packet. 
 
     
     
       12. The method of  claim 11  wherein said data transmitter comprises a universal serial bus power-delivery (USB-PD) transmitter residing in a first USB-capable device, said second transceiver comprises a USB-PD transceiver residing in a second USB-capable device, and said third transceiver comprises a USB-PD transceiver residing in a first USB cable plug of a USB cable. 
     
     
       13. The method of  claim 12  wherein said data transmitter is further operable to communicate with a fourth USB-PD transceiver residing in a second USB cable plug of said USB cable, and wherein said plurality of unique start-of-packet delimiters further comprises a third start-of-packet delimiter, and wherein said selecting one of said plurality of start-of-packet delimiters comprises selecting the third start-of-packet delimiter if the second and fourth transceivers are the only intended recipients of the data packet. 
     
     
       14. A method of specifying an intended recipient of a data packet to be transmitted, the method comprising:
 maintaining a first start-of-packet delimiter associated with a first one or more recipient transceivers; 
 maintaining a second start-of-packet delimiter associated with a second one or more recipient transceivers; 
 when constructing a data packet intended for said first one or more recipient transceivers, constructing said data packet using the first start-of-packet delimiter to demarcate the start of said data packet; and 
 when constructing a data packet intended for said second one or more recipient transceivers, constructing said data packet using the second start-of-packet delimiter to demarcate the start of said data packet; 
 wherein said recipient transceivers comprise universal serial bus power-delivery (USB-PD) transceivers. 
 
     
     
       15. The method of  claim 14  wherein said first one or more recipient transceivers comprises a first USB-PD transceiver residing in a USB-capable device, and said second one or more recipient transceivers comprises said first USB-PD transceiver and a second USB-PD transceiver residing in a USB cable plug of a USB cable. 
     
     
       16. A method of specifying an intended recipient of a data packet to be transmitted, the method comprising:
 maintaining a first start-of-packet delimiter associated with a first one or more recipient transceivers; 
 maintaining a second start-of-packet delimiter associated with a second one or more recipient transceivers; 
 when constructing a data packet intended for said first one or more recipient transceivers, constructing said data packet using the first start-of-packet delimiter to demarcate the start of said data packet; and 
 
       when constructing a data packet intended for said second one or more recipient transceivers, constructing said data packet using the second start-of-packet delimiter to demarcate the start of said data packet;
 maintaining a third start-of-packet delimiter associated with a third one or more recipient transceivers; 
 when constructing a data packet intended for said third one or more recipient transceivers, constructing said data packet using the third start-of-packet delimiter to demarcate the start of said data packet; 
 wherein said first one or more recipient transceivers comprises a first universal serial bus power-delivery (USB-PD) transceiver residing in a USB-capable device, said second one or more recipient transceivers comprises said first USB-PD transceiver and a second USB-PD transceiver residing in a first USB cable plug of a USB cable, and said third one or more recipient transceivers comprises said first USB-PD transceiver, said second USB-PD transceiver, and a third USB-PD transceiver residing in a second USB cable plug of said USB cable. 
 
     
     
       17. A universal serial bus (USB) device adapted to be coupled to a USB cable via a USB receptacle, the USB device comprising:
 the USB receptacle;   a controller coupled to the USB receptacle and configured to transmit a data packet including a start-of-packet (SOP) delimiter to demarcate the start of the data packet; and   wherein the data packet will only be accepted by the USB cable when the SOP delimiter transmitted by the controller matches a stored SOP delimiter stored in memory in the USB cable.   
     
     
       18. The USB device of claim 17, wherein the USB cable includes a USB cable controller configured to reject the transmitted data packet when the transmitted SOP delimiter does not match the stored SOP delimiter. 
     
     
       19. The USB device of claim 18, wherein the USB cable controller is configured to reject the transmitted data packet when a single bit in the transmitted SOP delimiter is different from a corresponding single bit of the stored SOP delimiter. 
     
     
       20. The USB device of claim 17, further comprising:
 a power switch having a first terminal adapted to be coupled to a power supply, a second terminal coupled to the USB receptacle, and a switch control input coupled to the controller; and   wherein the controller is configured to control the power switch to couple the power supply to the USB cable via the USB receptacle only after the USB cable accepts the data package.   
     
     
       21. A universal serial bus (USB) transceiver incorporated into a USB cable, the USB transceiver comprising:
 memory for storing a stored start-of-packet (SOP) delimiter; and   a processor coupled to the memory;   the USB transceiver is configured to receive a data packet including a SOP delimiter to demarcate the start of the data packet, and accept the data packet in response to the received SOP delimiter matching the stored SOP delimiter.   
     
     
       22. The USB transceiver of claim 21, wherein the USB transceiver is configured to reject the received data packet in response to the received SOP delimiter differing from the stored SOP delimiter.