Serial communication device with dynamic allocation of acceptance masks using serial implementation

Abstract

A CAN module or a microcontroller comprises a CAN module which receives a serial bit stream. The CAN module comprises a filter register with a bit select input and a single bit output, a bit select unit for selecting a bit of the filter register in accordance with the serial bit stream, a comparator coupled with the single bit output and with the serial bit stream for generating a comparison signal, and a register receiving the comparison signal for accumulating a plurality of comparison results and for generating an acceptance signal.

What is claimed is:  
     
         1 . A CAN module receiving a serial bit stream comprising: 
 a filter register having a bit select input and a single bit output;    a bit select unit for selecting a bit of said filter register in accordance with said serial bit stream;    a comparator coupled with said single bit output and with said serial bit stream for generating a comparison signal;    a register receiving said comparison signal for accumulating a plurality of comparison results and for generating an acceptance signal.    
     
     
         2 . CAN module according to  claim 1 , further comprising 
 a mask register having a bit select input and a single bit output;    a mask unit receiving said mask single bit output and said comparison result and generating a result signal being fed to said register.    
     
     
         3 . CAN module according to  claim 2 , further comprising 
 at least two mask register s having a bit select input and a single bit output;    a multiplexer for selecting one of said mask register single bit output s .    
     
     
         4 . CAN module according to  claim 3 , wherein said multiplexer comprises an input which is coupled with the single bit output of a further filter register.  
     
     
         5 . CAN module according to  claim 3 , wherein said multiplexer comprises an input which is coupled with a constant signal indicating no mask function.  
     
     
         6 . CAN module according to  claim 3 , wherein said multiplexer is controlled by at least one bit from said filter register.  
     
     
         7 . CAN module according to  claim 6 , wherein said filter register comprises two additional bits to control said multiplexer.  
     
     
         8 . CAN module according to  claim 1 , wherein said comparator is an EXCLUSIVE NOR gate.  
     
     
         9 . CAN module according to  claim 1 , wherein said mask unit is a NOR gate.  
     
     
         10 . CAN module according to  claim 1 , wherein said register is a D-Flip-Flop.  
     
     
         11 . A microcontroller comprising: 
 a central processing unit;    a random access memory connected to said central processing unit; and    a CAN module coupled with said central processing unit, wherein said CAN module comprises:    a filter register having a bit select input and a single bit output;    a bit select unit for selecting a bit of said filter register in accordance with said serial bit stream;    a comparator coupled with said single bit output and with said serial bit stream for generating a comparison signal;    a register receiving said comparison signal for accumulating a plurality of comparison results and for generating an acceptance signal.    
     
     
         12 . The microcontroller according to  claim 11 , further comprising: 
 a mask register having a bit select input and a single bit output;    a mask unit receiving said mask single bit output and said comparison result and generating a result signal being fed to said register.    
     
     
         13 . The microcontroller according to  claim 12 , further comprising: 
 at least two mask registers having a bit select input and a single bit output;    a multiplexer for selecting one of said mask register single bit outputs.    
     
     
         14 . The microcontroller according to  claim 13 , wherein said multiplexer comprises an input which is coupled with the single bit output of a further filter register.  
     
     
         15 . The microcontroller according to  claim 13 , wherein said multiplexer comprises an input which is coupled with a constant signal indicating no mask function.  
     
     
         16 . The microcontroller according to  claim 13 , wherein said multiplexer is controlled by at least one bit from said filter register.  
     
     
         17 . The microcontroller according to  claim 16 , wherein said filter register comprises two additional bits to control said multiplexer.  
     
     
         18 . The microcontroller according to  claim 11 , wherein said comparator is an EXCLUSIVE NOR gate.  
     
     
         19 . The microcontroller according to  claim 11 , wherein said mask unit is a NOR gate.  
     
     
         20 . The microcontroller according to  claim 11 , wherein said register is a D-Flip-Flop.  
     
     
         21 . A method of operating a CAN module comprising the steps of: 
 receiving a data stream;    generating an identifier and data out of said data stream;    comparing said identifier with a filter value on a bit by bit base;    generating an acceptance signal if said comparison is positive;    storing associated data in a buffer upon generation of said acceptance signal.    
     
     
         22 . A method according to  claim 21 , further comprising the step of masking said comparison result on a bit by bit base.  
     
     
         23 . A method according to  claim 22 , further comprising the step selecting a mask value from a plurality of mask values.  
     
     
         24 . A method according to  claim 23 , wherein said filter value provides additional data information for selecting said mask value.  
     
     
         25 . A method according to  claim 23 , wherein said mask values is selected from a plurality of mask registers and filter registers.  
     
     
         26 . A method according to  claim 23 , wherein one mask value provides a non-masking function.