# Custom AHB Slave Integration in NOEL-V Generic (GRLIB GPL 2025.2) 

**URL:** <https://discourse.grlib.community/t/custom-ahb-slave-integration-in-noel-v-generic-grlib-gpl-2025-2/566>\
**Category:** NOEL-V\
**Created:** [9 June 2026 08:21 UTC](https://discourse.grlib.community/t/custom-ahb-slave-integration-in-noel-v-generic-grlib-gpl-2025-2/566 "2026-06-09T08:21:56Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![THEDARKHORSE](https://avatars.discourse-cdn.com/v4/letter/t/7993a0/32.png) [@THEDARKHORSE](https://discourse.grlib.community/u/THEDARKHORSE)\
**Post date:** [9 June 2026 08:21 UTC](https://discourse.grlib.community/t/custom-ahb-slave-integration-in-noel-v-generic-grlib-gpl-2025-2/566/1 "2026-06-09T08:21:56Z")

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Hello,

I am integrating a custom AHB slave into the NOEL-V Generic reference design (GRLIB GPL 2025.2) targeting a Xilinx ZCU102 board.

The custom slave is instantiated in noelvcore.vhd with:

- hindex = 9

- haddr = 16#A10#

- hmask = 16#FFF#

- nextslv updated accordingly

The slave HCONFIG is:

```auto
constant HCONFIG : ahb_config_type := (
  0 => ahb_device_reg(VENDOR_CONTRIB, 16#002#, 0, 0, 0),
  4 => ahb_membar(haddr, '0', '0', hmask),
  others => zero32
);

```

The module synthesizes successfully and is connected as:

```auto
ahb_adder0 : entity work.ahb_adder
  generic map (
    hindex => ADDER_HSINDEX,
    haddr => ADDER_HADDR,
    hmask => ADDER_HMASK
  )
  port map (
    rst => rstn,
    clk => clkm,
    ahbsi => ahbsi,
    ahbso => ahbso(ADDER_HSINDEX)
  );

```

A custom APB slave integrated using VENDOR\_CONTRIB works correctly and appears in GRMON “info sys”.

However, the AHB slave does not appear to be selected. Accesses to 0xA1000000 using GRMON mem/wmem do not reach the peripheral and reads return zero.

Could someone clarify:

1. The recommended procedure for adding a custom external AHB slave to noelv-generic.

2. Whether ahb\_membar or ahb\_iobar should be used for a simple register-based peripheral.

3. Any additional files or configuration tables that must be updated besides nextslv, hindex assignment, HCONFIG, and ahbso(hindex) connection.

Environment:

- GRLIB GPL 2025.2-b4298

- GRMON4 v4.1.1 Evaluation

- Xilinx ZCU102

- RHEL 9

Any guidance would be greatly appreciated.

Thank you.

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**Author:** ![joaquin.espana](https://avatars.discourse-cdn.com/v4/letter/j/3da27b/32.png) [@joaquin.espana](https://discourse.grlib.community/u/joaquin.espana)\
**Post date:** [25 August 2026 08:08 UTC](https://discourse.grlib.community/t/custom-ahb-slave-integration-in-noel-v-generic-grlib-gpl-2025-2/566/2 "2026-08-25T08:08:55Z")

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Hi,

Did you manage to get your slave integrated in the design? Sorry about the delay, June is typically an extremely busy month at Gaisler so I failed to see your message.

Regards,  
Joaquín

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<div class="post-metadata">

**Author:** ![THEDARKHORSE](https://avatars.discourse-cdn.com/v4/letter/t/7993a0/32.png) [@THEDARKHORSE](https://discourse.grlib.community/u/THEDARKHORSE)\
**Post date:** [26 August 2026 05:56 UTC](https://discourse.grlib.community/t/custom-ahb-slave-integration-in-noel-v-generic-grlib-gpl-2025-2/566/3 "2026-08-26T05:56:30Z")

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Hi Joaquin, yes, I was able to move forward with the AHB integration. In parallel, I also successfully completed the NOEL-V bring-up on the ZCU104 and identified a board-specific clock constraint issue. I documented the changes and shared them with the Gaisler team for review.