Honored Contributorin altera,is there any library guide datasheet just like virtex4_hdl.pdf in xilinx? the attached jpg shows elements in the device.i take it for granted there should be such a doc in altera.but i didn't find it.
Honored ContributorNope. Note that most of the "primitives" are done through MegaFunctions. Altera tends to take a different approach, in that these are more behavioral than true primitives. As an example, there's the altddio_in megafunction, which user's use for DDR output registers in the I/O cell(I think similar to the IDDR). The thing is that some older devices don't have true I/O cell DDR inputs, so this megafunction will just put them into the fabric. Likewise, I saw a user enable an option for their DDR megafunction that wasn't supported in the device they were targeting, so again, it moved it to fabric registers to achieve the same functionality. As long as it met the I/O timing requirements, this works just as well.
There are definite benefits to this as far as portability, and being able to instantiate something that meets the design's needs. There are certainly drawbacks too. For the designer that wants to get low-level and figure out some "non-standard" use of the primitives, this approach certainly makes it difficult.
