Dynamic address change for slave devices on a shared bus
View Patent ↗A master/slave data communication system in which a master device communicates with the slave devices by uniquely addressing each of the slave devices. In order to enhance the security of the data communication system, each slave device includes an address generator for generating unique addresses. Periodically, the master device requests that one or more slave device change its address. In response to the request, the addressed slave device increments its address generating algorithm to provide a new slave address. The master device also includes an algorithm that is synchronized with the slave address generating algorithm, whereby when the slave changes its address, it need not transmit the new slave address to the master device over the bus.
1. In a data communication system of the type in which a master device communicates over a shared data bus with one or more slave devices, where each slave device is identified by a unique address, the slave device comprising:
an address generator associated with said slave device, said address generator generating plural addresses so that the address of said slave device can be changed; and
said slave device is responsive to a command from the master device for changing the respective address thereof, and said slave device that processes said command controls its address generator for changing the address thereof, wherein said slave address includes a variable address bit portion and a fixed address bit portion.
2. The slave device of claim 1 wherein each said slave device includes a pseudorandom address generator.
3. The slave device of claim 2 wherein said master device includes an algorithm for deriving the addresses generated by the pseudorandom address generator of each said slave device, whereby the master device can predict a new slave address without transmitting the new slave address from the slave device to the master device.
4. The slave device of claim 1 wherein a value of said fixed address bit portion is unique to said slave device.
5. The slave device of claim 1 wherein the address generator includes a shift register and a non-volatile memory for storing a default address, said default address used to set said shift register with a start address defined by said default address.
6. The slave device of claim 5 wherein said slave device further includes a multiplexer associated with each register of said shift register, and said non-volatile memory stores signature bits applied to said multiplexer for defining a behavior of the shifting of address bits by said shift register.
7. The slave device of claim 6 wherein said address generator further includes combinational logic for processing the address bits output from said shift register to provide a different set of address bits.
8. The slave device of claim 5 wherein said shift register comprises a linear feedback shift register.
9. The slave device of claim 8 wherein said linear feedback shift register comprises a modified Galios linear feedback shift register.
10. The slave device of claim 1 wherein said shared bus comprises an I 2 C bus protocol.
11. The slave device of claim 10 further including a replaceable container for holding a material that is deposited on a print medium by a printer, and wherein said slave device and associated address generator is mounted to said replaceable container.
12. A master/slave data communication system, comprising:
a shared data bus;
a plurality of slave devices connected to said shared bus;
a master device connected to said shared bus, said master device programmed to communicate with said slave devices by commands, one command programmed in said master device is a change address command, said change address command not including a new address;
an address generator associated with each said slave device, said address generator generating plural addresses so that the address of each said slave device can be changed; and
each said slave device is responsive to a change address command from the master device for changing the respective address thereof, and said slave device that processes said change address command controls its address generator for changing the address thereof; and
said slave devices programmed to not communicate to said master the respective new address, wherein the address of each said slave device comprises a variable address bit portion and a fixed address bit portion, where the fixed address bit portion has a value that is unique to each slave device.
13. The master/slave data communication system of claim 12 wherein said address generator comprises a linear feedback shift register.
14. The master/slave data communication system of claim 12 wherein said master device is programmed with an algorithm that simulates the addresses of the address generator of each said slave device, and said master device is programmed to increment the algorithm when an address change command is transmitted on the bus and acknowledged by the addressed slave device.
15. The master/slave data communication system of claim 12 wherein the master device is programmed to transmit a command on said shared bus, with a slave address in the command that is known to be invalid, whereby if a response is received by the master device, the master device is programmed to consider the response is from an imposter slave device.
16. In a data communication system of the type in which a master device communicates over a shared data bus with one or more slave devices, where each slave device is identified by a unique address, the slave device comprising:
an address generator associated with said slave device, said address generator generating plural addresses so that the address of said slave device can be changed; and
said slave device is responsive to a command from the master device for changing the respective address thereof, and said slave device that processes said command controls its address generator for changing the address thereof,
wherein the address generator includes a shift register and a non-volatile memory for storing a default address, said default address used to set said shift register with a start address defined by said default address.
17. The slave device of claim 16 , wherein said address generator further includes a multiplexer associated with each register of said shift register, and said non-volatile memory stores signature bits applied to said multiplexer for defining a behavior of the shifting of address bits by said shift register.
18. The slave device of claim 17 , wherein said address generator further includes combinational logic for processing the address bits output from said shift register to provide a different set of address bits.
19. The slave device of claim 16 , wherein said shift register comprises a linear feedback shift register.
20. The slave device of claim 19 , wherein said linear feedback shift register comprises a modified Galios linear feedback shift register.
21. A master/slave data communication system, comprising:
a shared data bus;
a plurality of slave devices connected to said shared bus;
a master device connected to said shared bus, said master device programmed to communicate with said slave devices by commands, one command programmed in said master device is a change address command, said change address command not including a new address;
an address generator associated with each said slave device, said address generator generating plural addresses so that the address of each said slave device can be changed; and
each said slave device is responsive to a change address command from the master device for changing the respective address thereof, and said slave device that processes said change address command controls its address generator for changing the address thereof; and
said slave devices programmed to not communicate to said master the respective new address, wherein said address generator comprises a linear feedback shift register.