void 

 txinit 
 ( 
 void 
 ) 

 { 

 if 
 ( 
 txn 
 >= 
 TXBSZ 
 ) 

 sysdown 
 ( 
 200 
 ) 
 ; 
 // tx buffer overflow has been detected. 

 txn 
 = 
 0 
 ; 

 txr 
 = 
 TXBSZ 
 ; 

 }