# Problem with GC\_INSTANCE\_IDX in vip\_gpio

**URL:** <https://forum.uvvm.org/t/problem-with-gc-instance-idx-in-vip-gpio/492>\
**Category:** Bitvis VIP GPIO\
**Tags:** question, vip\
**Created:** [April 21, 2025, 11:22am UTC](https://forum.uvvm.org/t/problem-with-gc-instance-idx-in-vip-gpio/492 "2025-04-21T11:22:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Jorge](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@Jorge](https://forum.uvvm.org/u/Jorge)\
**Post date:** [April 21, 2025, 11:22am UTC](https://forum.uvvm.org/t/problem-with-gc-instance-idx-in-vip-gpio/492/1 "2025-04-21T11:22:03Z")

</div>

Hi,

I am facing an issue that I do not see how to solve. As starter, I just cloned today the latest version, just in case this issue was already fixed/addressed. I have testbench (TB) with two different test harnesses(THs), one for the DUT, and the other for the Golden version of the design. Each TH has multiple vvc\_gpio instances to control the different ports in my DUT and Golden components.  
In order to access each VVC, I have set generics into the THs and then I declare constants into my TB to access them via the VVC methods (and assigning them as well into the generics of the THs).  
Everything compiles without showing any error however, when I launch the simulation with Mentor tools (Modelsim and QuestaSim), I got the following error:

```auto
# ** Fatal: (vsim-3734) Index value 11 is out of range 0 to 9.
# Time: 0 ps Iteration: 0 Process: /tb_uvvm_b05/i_golden/i_gpio_vvc_b05_start/cmd_executor File: UVVM/script/../bitvis_vip_gpio/script/../src/gpio_vvc.vhd
# FATAL ERROR while loading design

```

11 is one of the constants that I have generated to reference a VVC via GC\_INSTANCE\_IDX. If I change the value to “-11”, then I got the following error, as expected, during simulation:

```auto
Value -11 of generic "GC_INSTANCE_IDX" is out of range 0 to 2147483647.
# ** Fatal: (vsim-3729) Value -11 of generic "GC_INSTANCE_IDX" is out of range 0 to 2147483647.
# Time: 0 ps Iteration: 0 Instance: /tb_uvvm_b05/i_golden/i_gpio_vvc_b05_start File: UVVM/script/../bitvis_vip_gpio/script/../src/gpio_vvc.vhd Line: 44
# FATAL ERROR while loading design

```

To my understanding, the range accepted for the VVCs generic GC\_INSTANCE\_IDX should be bigger than 0 to 9. Am I correct? and if so, how can I proceed in using values bigger than 9?

Thank you

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<div class="post-metadata">

**Author:** ![EspenTa](https://dub1.discourse-cdn.com/flex017/user_avatar/forum.uvvm.org/espenta/32/52_2.png) [@EspenTa](https://forum.uvvm.org/u/EspenTa)\
**Post date:** [April 21, 2025, 2:29pm UTC](https://forum.uvvm.org/t/problem-with-gc-instance-idx-in-vip-gpio/492/2 "2025-04-21T14:29:31Z")

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Hi,

Try changing this constant in the adaptations package inside uvvm\_util:  
C\_MAX\_VVC\_INSTANCE\_NUM : natural := 10;  
The limitation is there to reduce the memory usage, but you may increase it if needed.

Regards  
Espen

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<div class="post-metadata">

**Author:** ![Jorge](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@Jorge](https://forum.uvvm.org/u/Jorge)\
**Post date:** [April 21, 2025, 3:15pm UTC](https://forum.uvvm.org/t/problem-with-gc-instance-idx-in-vip-gpio/492/3 "2025-04-21T15:15:28Z")

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Hi EspenTa,

Thank you, that solved the issue.