The Research Of Multi-channel A/D Synchronized Transformation Technology Based On PCI Bus

Geologic structure under the seafloor can be known by prospecting the marine magnetotelluric field. The marine environment is special and complex, the signal which is measured in the marine magnetotelluric instrument mainly include two electric fields(Ex, Ey) which are vertical each other and three magnetic fields(Hx, Hy, Hz) which are vertical each other and the seafloor environment. Multi-channel signal acquisition and A/D transformation must be synchronized processed. How to improve the speed of signal acquisition and data transformation is an important aspect of designing the instrument. Surrounding this technology problem, this paper offers a resolution.The marine magnetotelluric instrument designed by China University of Geosciences (BeiJing) takes PC104 industrial personal computer as the main function unit, it sends command to every circuit unit, the signal of magnetotelluric and seafloor environment is recorded continuously. The signal acquired by the sensors and processed by the A/D would be sent to FPGA in order to change the serial signal into the parallel.PCI is 32-bit bus signal and its frequency is 33MHz, the speed of data transformation can be as high as 132 MB/s compared to 16MB/s the speed of ISA bus, besides the PC104 processor bus definition is compatible with PCI bus definition which offers the condition to improve the speed of data transformation of the instrument.Based on the marine magnetotelluric instrument's data acquisition unit, this paper proposes the method of using the flexible FPGA and PCI bus technology to design the interface and replace the original ISA bus interface in order to improve the speed of data transformation of the instrument. Feasibility of the method, function characteristic of the new method, realization purpose, technique and collectivity frame are discussed; the material process and the result of the research are presented in the paper.