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Altera_Forum's avatar
Altera_Forum
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14 years ago

CPLD VHDL problem

HI, I am trying to understand the operation of the following VHDL code. The cpld EPM2210 is attached to a processor bus (d0-d15 and A0-A15). When I do a double read 'word aligned' address rang...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

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At address 0xXXXXXX58 I expected 1267 and then F23C but I get 08FC and 08FC

WHY!!!!

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Look sharp. According to your code, either X"982b" or X"08fc" are send. Only the code starting with if(state_fifo = 2) then is active.

I also noticed, that the CPLD will possibly drive the bus, although not addressed. The output is only correctly tri-stated, if an "others" address is omitted before cs or rd are deasserted. Otherwise the last output word is hold permanently.