Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 11/27/2024
Public
Document Table of Contents

8.6.1. System Reset High Level Flow

The following diagram shows the overall flow for POR, cold, warm, and software-initiated resets. Pink arrows indicate the path that is taken when a POR request occurs. The blue arrows show the path that is taken when a cold reset request is asserted. The red arrows indicate the path that is taken when a warm reset request is asserted. The individual steps in the flow are discussed in later sections.

Figure 272. Reset Flow Diagram

At a high level, the HPS comes out of power-on-reset (POR) via the following sequence:

  1. The SDM brings the reset manager out of POR (sdm_to_aps_por_rst_n).
  2. The SDM optionally sets security settings in the secure manager or configures clocks in the clock manager.
  3. If asserted, the SDM releases the HPS from cold reset, followed by releasing the HPS from warm reset.
  4. The reset manager de-asserts all but the DSU, bridge, peripheral, and individual COREx warm resets.
  5. The reset manager waits until the power manager requests a DSU reset de-assertion, then de-asserts all DSU resets.
  6. The SDM sets either the RESET_MGR.CPUx_RESET_BASE_HIGH register, the RESET_MGR.CPUx_RESET_BASE_LOW register, or both registers to the desired boot address if a value other than 0x0 is required.
  7. The reset manager waits for the CPURSTRELEASE[CPUx_RELEASE] bit to be set by the SDM or the power manager to assert a CPUx release signal to bring an individual CPU(s) out of reset.
    • RAM initialization or clearing is done purely through SDM software. The reset manager is not involved.
  8. When a CPURSTRELEASE[CPUx_RELEASE] bit is set or the power manager requests a CPU reset de-assertion, the reset manager completes the reset de-assertion process.
    • Other CPUs remain in the warm reset state until their corresponding CPURSTRELEASE[CPUx_RELEASE] bit is set, or the power manager asserts another CPUx reset de-assertion request.
    • CPUx_RELEASE bits are automatically cleared 16 boot_clk cycles after the core reset has de-asserted.
  9. Required peripherals are brought out of reset by software.
    • Peripherals not required by an application may be left in reset.