I have a Raspberry Pi Pico implementation. With so many pins and state machines you can have up to 8 different frequencies.
https://github.com/dorsic/PicoDIV <https://github.com/dorsic/PicoDIV> .md > On 1 May 2022, at 00:46, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > > Modern CPLDs often have an internal state machine that configures the chip on > power up. Not all of these shutdown the internal state machine clock after > configuration is complete. Crosstalk from the internal clock/oscillator will > modulate the output of a divider. > IIRC the Coolrunner II chips shuts down its internal oscillator after powerup > configuration is completed. > > Similar crosstalk issues can occur with freerunning internal oscillators > within some microcontrollers. Simpler microcontrollers have no internal > oscillators and are thus better suited to precision timing applications. > > Bruce >> On 01/05/2022 09:43 g...@hoffmann-hochfrequenz.de wrote: >> >> >> Am 2022-04-30 21:33, schrieb Clint Jay: >>> I think the reason the PICDiv is so well regarded is because of the >>> specific chips used and the way the timers etc. are implemented in >>> them. >>> >>> So, an alternate chip outside of the Microchip PIC range just might not >>> be >>> capable of the performance. >> >> For me, the alternate chip is a Xilinx Coolrunner II with the following >> half page of VHDL code. For my board, there is also a phase comparator >> on the chip, options for different OCXOs / more frequencies and space >> for syncing an OCXO to an incoming 1 pps (not tested). >> Just 1 pps generation should fit into an X2C32 (i.e. half the size), to >> 200 MHz. >> Pulse precision is like a 74LVC flip flop. >> >> Cheers, Gerhard >> >> >> ---------------------------------------------------------------------------------- >> -- Company: Hoffmann RF & DSP >> -- Create Date: 09:09:37 08/08/2012 >> -- Module Name: ppps1_generator - Behavioral >> -- Target Devices: X2c64A-5VQ44 >> -- Additional Comments: Free firmware under BSD license >> ---------------------------------------------------------------------------------- >> >> library IEEE; >> use IEEE.STD_LOGIC_1164.ALL; >> use ieee.numeric_std.all; >> >> entity pps1_generator is >> Port( >> clk : in STD_LOGIC; >> RunAt100MHz : in STD_LOGIC; >> pps1_out : out STD_LOGIC; >> ); >> end pps1_generator; >> >> architecture Behavioral of pps1_generator is >> signal tctr : integer range 0 to 99999999; >> signal pw_ctr : integer range 0 to 199999; >> signal cycle_done : boolean; >> signal pw_done : boolean; >> >> function bool2sl(b : boolean) return std_logic is >> begin >> if b then >> return '1'; >> else >> return '0'; >> end if; >> end function bool2sl; >> >> begin >> u_div: process(clk) is >> begin >> if rising_edge(clk) then >> cycle_done <= (tctr = 0); -- pipeline the comparator >> >> if cycle_done >> then >> if RunAt100MHz = '1' then -- reload >> tctr <= 100000000 - 2; -- divide by 100 >> Meg >> else >> tctr <= 10000000 - 2; -- divide by 10 >> Meg >> end if; >> else >> tctr <= tctr - 1; >> end if; >> >> end if; -- rising_edge() >> end process u_div; >> >> -- produce the standard 20 usec pulsewidth >> >> u_pulsewidth : process(clk) is >> begin >> if rising_edge(clk) then >> if cycle_done then >> if RunAt100MHz = '1' then >> pw_ctr <= 19999; >> else >> pw_ctr <= 1999; >> end if; >> >> elsif pw_ctr /= 0 then >> pw_ctr <= pw_ctr - 1; >> end if; >> >> pps1_out <= bool2sl(pw_ctr /= 0); >> >> end if; -- rising_edge() >> end process u_pulsewidth; >> >> end Behavioral; >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an >> email to time-nuts-le...@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
