uZedboard PL clock is not working on simple example

[erlingrj]

Hi.

I am unable to use the 100 MHz internal oscillator on the Zedboard that is connected to the Y9 package pin. I have a quite simple example of a custom UART receiver that is just outputting the received byte to the LEDs. I have inserted debug probes and the clock is just constant = 0, i.e. no clock square wave. I have spent hours trying different voltage levels and regenerating the bitstream but to no end. An extremely frustrating experience as I have another simple design with appearantly the same I/O settings (a clk signal connected to Y9) which does work. Do anyone have an idea of how to debug this?

Below I will copy my constraints file and post some screenshots from Vivado. Thanks alot for any help

This is my constraints:
"

set_property PACKAGE_PIN U14 [get_ports {leds_0[7]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[7]}]
set_property PACKAGE_PIN U19 [get_ports {leds_0[6]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[6]}]
set_property PACKAGE_PIN W22 [get_ports {leds_0[5]}]
set_property PACKAGE_PIN V22 [get_ports {leds_0[4]}]
set_property PACKAGE_PIN U21 [get_ports {leds_0[3]}]
set_property PACKAGE_PIN U22 [get_ports {leds_0[2]}]
set_property PACKAGE_PIN T21 [get_ports {leds_0[1]}]
set_property PACKAGE_PIN T22 [get_ports {leds_0[0]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[5]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[4]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[3]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[2]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[1]}]
set_property IOSTANDARD LVCMOS33 [get_ports {leds_0[0]}]
set_property PACKAGE_PIN Y9 [get_ports {clk_0}]
set_property PACKAGE_PIN P16 [get_ports {reset_0}]
set_property IOSTANDARD LVCMOS18 [get_ports {clk_0}]
set_property IOSTANDARD LVCMOS18 [get_ports {reset_0}]

set_property PACKAGE_PIN Y11 [get_ports {rxd_0}]
set_property IOSTANDARD LVCMOS18 [get_ports {rxd_0}]
"

[bruce_karaffa · Accepted solution]

You cannot monitor a clock with an ILA clocked by the same clock.  It will always look like a constant value.  In addition, doing this forces the clock off of dedicated clock routing.  Some suggestions.  Use a MMCM from a Clock Wizard to derive the on-board clock from your input clock.  If you want to monitor the clock out of the clock wizard, divide it in logic and route this divided signal to the ILA.

[erlingrj]

Thanks Bruce!
That hadn't occured to me. It turns out that the actual problem was that I had specified active low reset, while the pushbutton serving is inverted wrt that