In a world in which every processing cycle is proportional to used energy and the amount of available energy is limited, it is especially important to optimize source code in order to achieve the best possible runtime. In this paper, we present a side-channel secure C framework performing elliptic curve cryptography and improve its runtime on three 16-bit microprocessors: the MSP430, the PIC24, and the dsPIC. To the best of our knowledge we are the first to present results for the PIC24 and the dsPIC. By evaluating different multi-precision and field-multiplication methods, and hand-crafting the performance critical code in Assembler, we improve the runtime of a point multiplication by a factor of up to 5.41 and the secp160r1 field-multiplication by 6.36, and the corresponding multi-precision multiplication by 7.91 (compared to a speed-optimized C-implementation). Additionally, we present and compare results for four different standardized elliptic curves making our data applicable for real-world applications. Most spectacular are the performance results on the dsPIC processor, being able to calculate a point multiplication within 1.7 – 4.9 MCycles.