Research On Real-time Floating Point Arithmetic Processor Of Silicon Pixel Chip

X-ray polarization satellites are an important research method of astrophysics.The detection system of the low-energy X-ray polarization satellite includes two parts,a micro-structured gas detector and a silicon pixel chip with sensing and readout functions.The Topmetal silicon pixel chip developed by Central China Normal University is one of the candidate chips for low-energy X-ray polarization satellites.At present,there are many readout electronics solutions for silicon pixel sensors at home and abroad.There are general data readout systems for large-scale experiments and special readout systems for small-scale experiments.Most readout schemes read out all data and then perform offline data processing.However,space X-ray polarization satellites are limited by factors such as radiation,detector volume,satellite computing power,satellite data transmission bandwidth and other factors.The large amount of data generated by silicon pixel sensors cannot be transmitted back to the ground,and universal high-performance satellites cannot be installed on the satellite.Computing equipment.Designing a dedicated processor to process data in real time,compress the amount of data,and reduce the amount of offline storage data is an important research direction.This paper designs a dedicated floating-point processor ASIC for silicon pixel chips,which is used to process silicon pixel sensor signals online in real time,realize online real-time calculation of background noise,and complete data screening to reduce data throughput.The processor mainly includes modules such as a data preprocessing module,a controller,a floating-point operation unit,a write-back address buffer,an instruction storage unit,and a data storage unit.The processor adopts the Harvard structure,the customized floating-point processing unit is specially used for background noise calculation,and the write-back address cache ensures continuous high-speed execution of instructions.The data preprocessing module converts the integer data sampled by the ADC into a single-precision floating-point number.In addition,a compiler is designed for the special instruction set of the processor to compile assembly code into machine instructions.The compiler is also responsible for checking data conflicts and optimizing the code.After simulation test,the compiler designed in this paper compiles assembly instructions into machine code correctly and completely,and can detect and resolve data conflicts.At a working frequency of 50MHz,when the processor is processing actual detection data,the calculated background noise error is 0.007%,and the peak operation speed of the processor is 40MFLOPS,which fully meets the requirements of silicon pixel chips.Using 130nm CMOS process to complete the physical design and implementation,the final layout area is about 4.58mm2,and the static power consumption is about 36mW.This design will be applied to the X-ray polarization detection micro-nano satellite based on silicon pixel chip.