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12435 Discussions

clearing fifo and blocking call to fifo

Honored Contributor II



I have an avalon-ST source streaming data into a onchip FIFO (ST input & MM output). Currently the Nios reads blocks of data using a call to 'altera_avalon_fifo_read_fifo()' and places it into an array to perform a computation. At the first call, the FIFO is already filled up. After processing a block or two it catches up and I am reading zero between valid data samples. 


First question - is there a way to empty the contents of my onchip FIFO without reading out the data? Alternatively, can the FIFO be disabled by default until the Nios enables it through a status register? 


Second question - without using interrupts, can I make a blocking call to read the fifo? In other words, how can I force the Nios to wait until the FIFO has a new data sample? 




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2 Replies
Honored Contributor II

Answering the 2nd question: Loop reading the fifo status until it reports 'data available'. I guess the altera_avalon_fifo_read_fifo() returns the amount read?

Honored Contributor II

It doesn't look like the FIFO supports flushing. By disabling do you mean disable it from accepting streaming data until enabled? If so then it doesn't look like it supports that either. 


Normally I build my own FIFOs when I need additional functionality. Luckily they are easy to build so maybe that would be your best bet to do.