An efficient way of multirate asynchronous data transfer in MicroBlaze™ processor for GNSS receiver

This paper presents a novel for asynchronous data transfer of correlation values in Navigation receiver implemented with novel approach of using FPGA and MicroBlaze™ soft-core processor. The design consists of 14 channel receiver with correlators in FPGA logic and discriminators and loop filters in MicroBlaze™ Processor. This approach needs transfer of data with asynchronous clock domains between FPGA and MicroBlaze™ processor. In each channel, there are six correlation values to be transferred from FPGA logic to MicroBlaze™ processor. These correlation values are processed by MicroBlaze™ processor and feedback is provided to control code and carrier frequency and phase for each channel. The data transfer in this case is time bound as there are many close loop control systems and any error or time lag in the system may lead to loss of signal lock or degradation in the performance. The correlation values change at different instances and rate in different channels so use of FIFO for such application is not suitable. A new approach has been devised for data transfer between FPGA and MicroBlaze™ processor. This paper describes the approach with its advantages compared to conventional FIFO based approach.