On a keyboard,a key include 4 letters ,likes '1','A','B','C' being input in different time by a key.I use Timer0 interrupt service routine as a keyboard_scaning , which interval is 50ms and a valid char will be scaned two times.and i use Timer1 as delay_counter .for example,scaning '1' Key the first time by T0_isr,key_temp is '1',release '1' key and closed immediately ,just the same key be scaned the second time,key_temp is 'A'.when the key release ,Timer1 is enabled.the T1_isr will give a valid Key 'A' to main program after the delay_time.It is clearly a delay_time between key_releasing to Timer1 flowing to ensure the Key 'A' is valid. In the other words ,every Key must wait for delay_time when input. and now ,I want not to waiting the delay_time if the next closed Key is not the same previous Key,how can cancel delay_time between two different Keys? Can you tell me how to do ?Have any source code for example? Best regards, Nantiangumo