when I say partial word access, I mean 16-bit (two byte) or 8-bit (byte) read/write.
Background:
In one of our recent projects, Cyclone V SoC is used to replace 386 CPU in an existing product.
I am responsible for the board and FPGA design. Another software engineer is developing software under DS5 environment.
Avalon MM Slave interface is use on FPGA side.
Problem description:
Everything works fine on Altera System Console. However, it behaves differently when the software engineer debug his code on DS5.
He has problem to read data out from an address that is not multiple of 4.
For example, he can read a word (32-bit), or a half-word (16-bit), or a byte from address 0x800, but he cannot read anything from address 0x802 (always returned zeros).
Troubleshooting being conducted:
I thought it relates to where the data should be put on the 32bit data bus. So I revised FPGA code to duplicate the data on the 32-bit bus,
but DS5 still reads all zeros.
Also tried to run SignalTap to capture waveforms, but DS5 and SignalTap
cannot be run at the same time through the same JTAG connector.
anybody know what could be the problem? |
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