Commit 3f142deb authored by serrano's avatar serrano

First quick assessment of some of the files.


git-svn-id: http://svn.ohwr.org/fmc-tdc@67 85dfdc96-de2c-444c-878d-45b388be74a9
parent 49fc1bea
Disclaimer: not enough time to do this design justice. Looking at VHDL
constructs independently, not trying to make sense of the design as a
whole.
top_tdc.vhd
===========
- Line 1057 (and others). The wait until spec_clk = '1'; at the end of
the process looks awkward to me. I guess it means this is a
synchronous process working on the rising edge of spec_clk. Is there
any advantage to using this notation?
acam_databus_interface.vhd
==========================
- Line 73. "read" and "write" are not VHDL reserved words but they are
names of functions people use to do I/O. Probably wise to chose
other names for states.
- Line 244. address_o going to the ACAM is not registered. This signal
is driven by adr_i, the wishbone input address. These lines are
being used in another entity (data_engine.vhd) as inputs to other
processes so chances are they will not use IOB FFs, which might be
important to respect setup and hold constraints of the ACAM.
acam_timecontrol_interface.vhd
==============================
- Line 246 (and others). This can be written in one line:
"start_trig_r <= start_trig & start_trig_r(1 downto 0);"
- Line 255 (and others). This edge detector uses signal ref_clk_r(3),
which is potentially metastable. It also relies very heavily on the
fact that ref_clk should be at a given frequency.
clk_rst_managr.vhd
==================
Line 284. This process can create metastability in signal gral_incr,
which is then going to many destinations inside the incr_counter
block, possibly leading to non-deterministic behavior of the counter.
Line 309. Signal cs seems to be negative logic. This should be visible
in its name.
Line 571. cs will not use an IOB FF because it is read in line
366. Please check all other cases when this can happen.
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