In modern cryptographic systems, physical unclonable functions (PUFs) are efficient mechanisms for many security applications, which extract intrinsic random physical variations to generate secret keys. The classical PUFs mainly exhibit static challenge-response behaviors and generate static keys, while many practical cryptographic systems need reconfigurable PUFs which allow dynamic keys derived from the same circuit. In this paper, the concept of reconfigurable multi-port PUFs (RM-PUFs) is proposed. RM-PUFs not only allow updating the keys without physically replacement, but also generate multiple keys from different ports in one clock cycle. A practical RM-PUFs construction is designed based on asynchronous clock and fabricated in TSMC low-power 65nm CMOS process. The area of test chip is 1.1mm², and the maximum clock frequency is 0.8GHz at 1.2V. The average power consumption is 27.6mW at 27°C. Finally, test results show that the RM-PUFs generate four reconfigurable 128-bit secret keys, and the keys are secure and reliable over a range of environmental variations such as supply voltage and temperature.