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[Discuss-gnuradio] GPIF bus cycle waveform

From: Kalen Watermeyer
Subject: [Discuss-gnuradio] GPIF bus cycle waveform
Date: Sun, 16 Jul 2006 18:40:58 +0100 (BST)


After looking through the FX2 data sheet, the GPIF
designer app's generated code and your edit_gpif
script output, I (hope) I have an understanding of the
actual data flow bus cycle (I am only focusing on

You use flow states. There is a flowstate in state S1,
which constantly asserts REN and OE (and BOGUS) while
the transaction has not yet expired. 
It deasserts all CTLx signals when the transfer is

You do data transfers on both edges of IFCLK. the
FLOWSTB register indicates that CTL4 is your master
strobe - is this correct? I thought CTL4 was a reset
signal (CLRST).

I have tried to meet these requirements in my
firmware, but it is a little buggy. I also had a look
at the verilog code (bus_interface.v) to see how your
GPIF signalling works, but only have experience with

To summarise:
OE and REN are active-high, and data is clocked out on
both edges of IFCLK. 

What part do the RDYx pins play in the flowstate? Or
do they only affect transitions between S1, S2..S6?

I'm really close to getting this thing working, but
for a clearer understanding of the signalling over the

Thanks again

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