COMMUNICATION BETWEEN AN IMAGE FORMING DEVICE AND A REPLACEABLE SUPPLY ITEM
FIG2 is a block diagram depiction of the image forming device including a communication bus that permits communication between a controller of the image forming device and one or more supply chips according to one example embodiment  FIG1 is a schematic view of an image forming device having one or more replaceable supply items according to one example embodiment
FIG2 shows a communication bus 30 of image forming device 10 that facilitates communication between controller 20 and supply chips 110 according to one example embodiment. FIG2 shows one supply item 100 and associated supply chip 110 in solid line and an additional supply item lOOn and associated supply chip 110n in broken line indicating that additional supply items 100 having supply chips 110 may be used as desired. In the example embodiment illustrated, communication bus 30 utilizes the Inter-Integrated Circuit (I2C) protocol; however, other communication protocols may be used as desired. Controller 20 is configured to serve as the master node of communication bus 30 with each supply chip 110 configured to serve as a respective slave node. In the example embodiment illustrated, a system chip 22 serves as an additional slave node of communication bus 30. In this embodiment, controller 20 and system chip 22 combine to form a control unit 24 of image forming device 10 that controls communication with supply chips 110. In one embodiment, system chip 22 facilitates encrypted communication between controller 20 and supply chips 110 where controller 20 and supply chips 110 are unable to directly interpret messages from each other for security purposes. For example, prior to sending an encrypted command to a supply chip 110, controller 20 may send the command to system chip 22 which may decrypt and re-encrypt the command according to a format that will be understood by supply chip 110 and return the re-encrypted command to controller 20 to be sent by controller 20 to supply chip 110. Similarly, upon receiving an encrypted response from a supply chip 110, controller 20 may send the response to system chip 22 which may decrypt and re-encrypt the response according to a format that will be understood by controller 20 and return the re-encrypted response to controller 20. System chip 22 may also aid controller 20 in the authentication and validation of supply chips 110.  Referring now to the drawings and particularly to FIG1, there is shown a schematic depiction of an image forming device 10 according to one example embodiment. Image forming device 10 may include, for example, an electrophotographic printer (commonly referred to as a laser printer), which may include scanning, copying or faxing functionality. One or more supply items 100 are removably installed in image forming device 10 allowing a user to replace or repair supply items 100 as needed in order to continue printing. For example, FIG1 shows an access door 12 on image forming device 10 that opens to allow a user to install or remove supply items 100 from image forming device 10. In the example embodiment illustrated, each supply item 100 includes a reservoir 102 formed within a housing 104 of the supply item 100 for holding a supply of toner for use in print operations by image forming device 10. However, supply item 100 may include any component requiring periodic user replacement such as, for example, a fuser of an electrophotographic printer, a waste toner container that stores unused toner removed from a photoconductive drum or intermediate transfer member of an electrophotographic printer, etc.
block diagram, schematic view
24
control unit
30
communication bus
12
access door
22
system chip
100
supply item supply items
20
controller
34
clock line
102
reservoir
10
image forming device
110
supply chip supply chips
32
data line
['1. A method of electrical communication between a slave node of an I2C communication bus positioned on a replaceable supply item installed in an image forming device and a controller of the image forming device as a master node of the I2C communication bus, comprising: receiving a first write command by the slave node on the replaceable supply item from the controller of the image forming device; comparing by the slave node on the replaceable supply item a value of a transmission cycle bit contained in a header of the first write command with a value of a transmission cycle bit contained in a header of a second write command received by the slave node on the replaceable supply item from the controller of the image forming device previous to the first write command; and if the value of the transmission cycle bit contained in the header of the first write command is equal to the value of the transmission cycle bit contained in the header of the second write command, sending by the slave node on the replaceable supply item to the controller of the image forming device a response to the second write command without executing the first write command.']