void 

 txput0 
 ( 
 byte 
 ch 
 ) 

 { 

 // to reduce the cpu consumption, 

 // venture to omit txn overflow check. 

 // if programmed properly, such an overflow never occurs. 

 // rxn(appears later) check is omitted as well. 

 txbuf 
 [ 
 txn 
 ++ 
 ] 
 = 
 ch 
 ; 

 txcrc 
 = 
 0 
 ; 

 } 



 void 

 txput1 
 ( 
 byte 
 ch 
 ) 

 { 

 txbuf 
 [ 
 txn 
 ++ 
 ] 
 = 
 ch 
 ; 

 txcrc 
 = 
 crctbl 
 [ 
 txcrc 
 ^ 
 ch 
 ] 
 ; 

 } 



 void 

 txputcrc 
 ( 
 boolean 
 force_error 
 ) 

 { 

 txput0 
 ( 
 ( 
 force_error 
 ) 
 ? 
 ++ 
 txcrc 
 : 
 txcrc 
 ) 
 ; 

 }