At the end, I had to check the disassembly listing and replace those poor optimized C sentences with ASM blocks.
The generated code was running in 230 instruction cycles. The XC8 was far from being efficient enough to fit the algorithm. Could the C compiler be efficient enough to make the algorithm to run in just those 120 cycles I had? I estimated between 30 and 40 cycles if I code it in ASM, so I was asking for a C compiler just 25% or 33% as efficient as programming in assembly. Running at 16MHz, I calculated I had 120 instructions cycle to execute the algorithm: getting the CCP1 comparator value, checking if it has only a small deviation from the past captured values, calculating the median and storing it in a buffer. The firmware has a time-critical section were an algorithm is executed to measure the frequency of a signal.
I have been working for the past week in a new design and as my most important requirement is the size of the PCB, I decided to use the new PIC 12F1840. Today I am only going to write shortly about how the free mode of the XC8 compiler bloats the binary to make the Pro version look more efficient. In those optimizations I have seen weird things made by compilers and I have been long time wanting to write about it. However, I program the PIC18 devices in C but I often had to dive into the asm of the generated binary to optimize it. I still use ASM to program the PIC12 and PIC16 family. With this movement, Microchip provide to their clients a cheap and decent C compiler as their old and deprecated C18 compiler was - in my opinion - plenty of bugs and not worthy to work with. Few memory, scarce resources, small instructions set, few addressing modes… Anyway, who needs a C compiler with such simple architectures? Two years ago Microchip bought the Hi-Tech company and renamed their Picc compiler as XC8. Those cores were so simple that it was not easy no make a C compiler for them. But the fault was not in the compilers manufacturers, but in the PIC core architecture. As far as I remember, only Hi-Tech, IAR and CCS had compilers - not even Microchip has his own one - and they were quite horrible compiling. When I started to program PICs microcontrollers in 1998 there was not too many options to program PICs in C. In fact, I even used to hate it due to the poor quality of the C compilers. Hot pursuit 2010 cd key generator.Īnd why it is using LSRF to perform the first rotation and it is using BCF CARRY + RRF in the next rotations? Xbox Live Code Generator. Crude Reality: Petroleum in World History Exploring World History eBook: Brian C. In fact, the variable is rewritten in another non-sense operation like this one in the next 10 instructions. ※ Download: ?dl&keyword=mplab+xc8+pro+keygen&source=
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