四线电阻式触摸屏

				
				State Machine - |Block1|ADS7846a:inst|state
				Name state.wait_300ms state.read_bit state.write_bit state.control state.reset 
				state.reset 0 0 0 0 0 
				state.control 0 0 0 1 1 
				state.write_bit 0 0 1 0 1 
				state.read_bit 0 1 0 0 1 
				state.wait_300ms 1 0 0 0 1