Subject: Re: [Fpga2600] Re: [stella] TIA schematic question From: Adam Wozniak <adam@xxxxxxxxxxxxxxxx> Date: Mon, 15 Nov 2004 11:10:01 -0800 (PST) |
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Mon, 15 Nov 2004, Chris Wilkson wrote: > Those are master-slave flipflops. If you look at the F1 cell, there are > 2 s-r latches there. At no time are both those latches open. The first > one (driven by the nor gates) is open only when clock is low. The second > one is open only when clock is high. Ok, I see it now. What am I doing wrong here then? entity bb_boxf1 is port ( clock : in std_logic; q : out std_logic; notq : out std_logic; reset : in std_logic; notr : in std_logic; nots : in std_logic); end bb_boxf1; architecture behavioral of bb_boxf1 is signal tmp1 : std_logic; signal tmp2 : std_logic; signal tmp3 : std_logic; signal tmp4 : std_logic; signal tmp5 : std_logic; signal tmp6 : std_logic; signal tmp7 : std_logic; signal tmp8 : std_logic; begin tmp1 <= not (clock or nots); tmp2 <= not (clock or notr); tmp3 <= not (tmp1 or tmp4); tmp4 <= not (tmp2 or reset or tmp3); tmp5 <= clock and tmp3; tmp6 <= clock and tmp4; tmp7 <= not (tmp5 or reset or tmp8); tmp8 <= not (tmp7 or tmp6); q <= tmp7; notq <= tmp8; end behavioral; Do I need to rewrite this to be a little more straightforward? Maybe more like this (untest code ahead, may contain syntax errors...) architecture behavioral of bb_boxf1 is signal tmp1 : std_logic; signal tmp2 : std_logic; begin procedure (clock) begin if (clock'event and clock = '0') then if (nots = '0') then tmp1 <= '1'; elsif (notr = '0') then tmp1 <= '0'; end if; end if; end procedure; procedure (clock) begin if (clock'event and clock = '1') then if (reset = '1') then tmp2 <= '0'; else tmp2 <= tmp1; end if; end if; end procedure; q <= tmp2; notq <= not tmp2; end behavioral; - -- adam@xxxxxxxxxxxxxxxx http://cuddlepuddle.org/~adam KG6GZR http://cuddlepuddle.org/~adam/resume.html "Feminist? Why would I want to alienate half the population? I'm an egalitarian." -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFBmP7dyvXf5Z0z5zERAkSSAKCQPfmJP7KK29kUKW9ijRRcIEDYGQCgj+i7 HzV259anvKm1Rl1w7QqddF4= =rN3M -----END PGP SIGNATURE-----
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