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VHDL - Problem with H,Z and inout signals |
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#1 |
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Hello everybody,
I have a little problem with my VHDL code. I have a situation like the following one: pinout/signal_a <--> block_1/signal_b <--> block_2/signal_c where <--> indicate an inout port. The code looks something like that: signal_a <= local_signal And on the module that has signal_b as output I put: signal_b => local_signal During simulation I obtain that when signal_a is H (the expected result), while signal_b and signal_c are Z, while when the signal_a is 0, signal_b and signal_c are coherent. The Z value is put on the signal_c by the block_2 and propagated to signal_b, while signal_a is connected to a pullup and forced to the value H when it is not 0. Reading the VHDL standard I found out that the resolution functions imposes that when the same line is drove by H and Z the resulting signal is H. Is there something I'm missing? The signals are of type std_logic/std_logic_vector (signal_a is a single wire of a std_logic_vector). Any help will be appreciated. Gio. Giox |
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#2 |
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Posts: n/a
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Giox wrote:
> Is there something I'm missing? I don't understand the question. Post your code. Here is a sim example that tests a tri-state node: http://home.comcast.net/~mike_treseler/oe_demo.vhd -- Mike Treseler Mike Treseler |
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