Window Watchdog Timer (WDT0 / WWDT) model for ra8_emulator. More...

#include <stdint.h>
#include <stdio.h>
#include "board_periph.h"
#include "board_periph_block.h"
#include "emu_host_io_internal.h"

Include dependency graph for board_periph_wdt.c:

Data Structures
struct	wdt_state_t
	WDT model state. More...

Enumerations
enum	wdt_geom_t : uint64_t { k_wdt_base = 0x40202600UL , k_wdt_span = 0x10UL , k_wdt_off_wdtrr = 0x00UL , k_wdt_off_wdtcr = 0x02UL , k_wdt_off_wdtsr = 0x04UL , k_wdt_off_wdtrcr = 0x06UL }
	WDT0 block geometry (ra8_wdt_regs.h, r_wdt_regs_t). More...
enum	wdt_field_t : uint32_t { k_wdt_refresh_a = 0x00U , k_wdt_refresh_b = 0xFFU , k_wdt_rcr_rstirqs = 0x80U , k_wdt_sr_cntval = 0x3FFFU , k_wdt_sr_undff = 0x4000U , k_wdt_timeout_ticks = 400U }
	WDT register field constants (ra8_wdt_regs.h). More...
enum	wdt_order_t : uint32_t { k_wdt_block_order = 180U }
	Per-tick order slot for the WDT block (relative order only). More...

Functions
static RA8_INTERNAL void	internal_wdt_tick (uc_engine *uc)
	Per-chunk advance: run the armed down-counter; reset on underflow.
static RA8_INTERNAL void	internal_wdt_reset (void)
	Reset the WDT model to power-on state.
static RA8_INTERNAL uint64_t	internal_wdt_read (uc_engine *uc, uint64_t addr, unsigned size)
	MMIO read inside the WDT window.
static RA8_INTERNAL void	internal_wdt_write (uc_engine *uc, uint64_t addr, unsigned size, uint64_t value)
	MMIO write inside the WDT window.
static RA8_INTERNAL void	internal_wdt_report (void)
	End-of-run WDT section: refreshes and whether it fired a reset.
static RA8_INTERNAL void	internal_wdt_block_register (void)
	Register the WDT0 block before main (host constructor).

Variables
static wdt_state_t	s_wdt
static const board_periph_block_t	s_k_wdt_block
	WDT0 block descriptor (self-registered with the core).

Detailed Description

Window Watchdog Timer (WDT0 / WWDT) model for ra8_emulator.

Models the RA8D2 WDT0 (ra8_wdt_regs.h, ra8_wdt.c) at 0x40202600 closely enough that a watchdog reset actually fires when the firmware stops refreshing the counter, instead of the timeout never happening. Against the sparse fallback wdt_reset_recovery_demo armed the WWDT for reset and then stopped refreshing, but the chip never reset, so the post-reset boot (and its "wdt: reset_by=watchdog" banner) was unreachable. This block runs the down-counter and, on underflow in reset mode, asks the run loop to warm-reboot the firmware with the watchdog-reset cause latched, so the next boot reads k_ra8_reset_cause_wdt0.

Behaviour (HUM Ch 27.2):

WDTRR (0x00) is the refresh register: the 0x00 then 0xFF unlock sequence both ARMS the counter (the first refresh starts it) and RELOADS it to full. A stray write that breaks the sequence is ignored here (the model does not synthesise the refresh-error path).
WDTCR (0x02) selects the timeout period (TOPS); shadowed so a read back works. The board emulator has no real watchdog clock, so the timeout maps to a fixed number of emulation ticks (one tick == one run-loop chunk): large enough that a normally-refreshing app stays alive, small enough that a deliberate stop trips within the run budget.
WDTSR (0x04) reports the live down-counter in CNTVAL and the UNDFF underflow flag.
WDTRCR (0x06) RSTIRQS selects reset (1) vs NMI / IRQ (0) on underflow.

The per-chunk tick hook decrements the counter once it is armed; when it reaches zero with RSTIRQS set, it raises the reboot request and disarms (so it fires exactly once). With RSTIRQS clear (NMI / IRQ mode), the underflow latches UNDFF but does not reboot – the board emulator does not route the WDT NMI.

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since: 0.1.0

Definition in file board_periph_wdt.c.

Enumeration Type Documentation

◆ wdt_field_t

enum wdt_field_t : uint32_t

WDT register field constants (ra8_wdt_regs.h).

Enumerator
k_wdt_refresh_a	First byte of the refresh sequence.
k_wdt_refresh_b	Second byte of the refresh sequence.
k_wdt_rcr_rstirqs	WDTRCR.RSTIRQS: 1 = reset on underflow.
k_wdt_sr_cntval	WDTSR.CNTVAL[13:0] live counter.
k_wdt_sr_undff	WDTSR.UNDFF underflow flag (bit 14).
k_wdt_timeout_ticks	Wdt timeout ticks.

Definition at line 58 of file board_periph_wdt.c.

◆ wdt_geom_t

enum wdt_geom_t : uint64_t

WDT0 block geometry (ra8_wdt_regs.h, r_wdt_regs_t).

Enumerator
k_wdt_base	WDT0 base (HUM Ch 27).
k_wdt_span	Covers WDTRR..WDTRCR.
k_wdt_off_wdtrr	WDTRR refresh register (8b).
k_wdt_off_wdtcr	WDTCR control (16b).
k_wdt_off_wdtsr	WDTSR status (16b).
k_wdt_off_wdtrcr	WDTRCR reset control (8b).

Definition at line 48 of file board_periph_wdt.c.

◆ wdt_order_t

enum wdt_order_t : uint32_t

Per-tick order slot for the WDT block (relative order only).

Enumerator
k_wdt_block_order	After the reset block; report order.

Definition at line 71 of file board_periph_wdt.c.

Function Documentation

◆ internal_wdt_block_register()

RA8_INTERNAL void internal_wdt_block_register ( void )

static

Register the WDT0 block before main (host constructor).

Definition at line 230 of file board_periph_wdt.c.

References board_periph_register_block(), RA8_INTERNAL, and s_k_wdt_block.

◆ internal_wdt_read()

RA8_INTERNAL uint64_t internal_wdt_read	(	uc_engine *	uc,
		uint64_t	addr,
		unsigned	size )

static

MMIO read inside the WDT window.

MMIO read inside the wdt window; this step is contained within the board periph watchdog model and uses bounded caller or module-owned storage.

Parameters

[in,out]	uc	Unicorn engine whose emulated state is read or updated.
[in]	addr	Guest address involved in the operation.
[in]	size	Size of the requested region or access in bytes.

Returns: The watchdog read result produced by the board periph watchdog model.

Return values

value The operation-specific watchdog read value.

Precondition: Arguments satisfy the ranges documented for watchdog read.; The call executes on the emulator's single owning thread.

Postcondition: State changes remain confined to the board periph watchdog model and documented output objects.; Ownership of caller-supplied storage is unchanged.

Note: The operation is synchronous and does not transfer heap ownership.

Since: 0.1.0

Definition at line 144 of file board_periph_wdt.c.

References k_wdt_base, k_wdt_off_wdtcr, k_wdt_off_wdtrcr, k_wdt_off_wdtsr, k_wdt_sr_cntval, RA8_INTERNAL, and s_wdt.

◆ internal_wdt_report()

RA8_INTERNAL void internal_wdt_report ( void )

static

End-of-run WDT section: refreshes and whether it fired a reset.

End-of-run wdt section: refreshes and whether it fired a reset; this step is contained within the board periph watchdog model and uses bounded caller or module-owned storage.

Precondition: Arguments satisfy the ranges documented for watchdog report.; The call executes on the emulator's single owning thread.

Postcondition: State changes remain confined to the board periph watchdog model and documented output objects.; Ownership of caller-supplied storage is unchanged.

Note: The operation is synchronous and does not transfer heap ownership.

Since: 0.1.0

Definition at line 205 of file board_periph_wdt.c.

References priv_emu_io_errf(), RA8_INTERNAL, and s_wdt.

◆ internal_wdt_reset()

RA8_INTERNAL void internal_wdt_reset ( void )

static

Reset the WDT model to power-on state.

Reset the wdt model to power-on state; this step is contained within the board periph watchdog model and uses bounded caller or module-owned storage.

Precondition: Arguments satisfy the ranges documented for watchdog reset.; The call executes on the emulator's single owning thread.

Postcondition: State changes remain confined to the board periph watchdog model and documented output objects.; Ownership of caller-supplied storage is unchanged.

Note: The operation is synchronous and does not transfer heap ownership.

Since: 0.1.0

Definition at line 126 of file board_periph_wdt.c.

References RA8_INTERNAL, and s_wdt.

◆ internal_wdt_tick()

RA8_INTERNAL void internal_wdt_tick ( uc_engine * uc )

static

Per-chunk advance: run the armed down-counter; reset on underflow.

Per-chunk advance: run the armed down-counter; reset on underflow; this step is contained within the board periph watchdog model and uses bounded caller or module-owned storage.

Parameters

[in,out] uc Unicorn engine whose emulated state is read or updated.

Precondition: Arguments satisfy the ranges documented for watchdog tick.; The call executes on the emulator's single owning thread.

Postcondition: State changes remain confined to the board periph watchdog model and documented output objects.; Ownership of caller-supplied storage is unchanged.

Note: The operation is synchronous and does not transfer heap ownership.

Since: 0.1.0

Definition at line 98 of file board_periph_wdt.c.

References board_periph_reset_request_reboot(), k_wdt_rcr_rstirqs, k_wdt_sr_undff, RA8_INTERNAL, and s_wdt.

◆ internal_wdt_write()

RA8_INTERNAL void internal_wdt_write	(	uc_engine *	uc,
		uint64_t	addr,
		unsigned	size,
		uint64_t	value )

static

MMIO write inside the WDT window.

MMIO write inside the wdt window; this step is contained within the board periph watchdog model and uses bounded caller or module-owned storage.

Parameters

[in,out]	uc	Unicorn engine whose emulated state is read or updated.
[in]	addr	Guest address involved in the operation.
[in]	size	Size of the requested region or access in bytes.
[in]	value	Register or payload value involved in the operation.

Precondition: Arguments satisfy the ranges documented for watchdog write.; The call executes on the emulator's single owning thread.

Postcondition: State changes remain confined to the board periph watchdog model and documented output objects.; Ownership of caller-supplied storage is unchanged.

Note: The operation is synchronous and does not transfer heap ownership.

Since: 0.1.0

Definition at line 175 of file board_periph_wdt.c.

References k_wdt_base, k_wdt_off_wdtcr, k_wdt_off_wdtrcr, k_wdt_off_wdtrr, k_wdt_refresh_a, k_wdt_refresh_b, k_wdt_timeout_ticks, and s_wdt.

Variable Documentation

◆ s_k_wdt_block

const board_periph_block_t s_k_wdt_block

static

Initial value:

                                                = {
  .base   = (uint64_t)k_wdt_base,
  .span   = (uint64_t)k_wdt_span,
  .order  = (uint32_t)k_wdt_block_order,
  .read   = internal_wdt_read,
  .write  = internal_wdt_write,
  .tick   = internal_wdt_tick,
  .reset  = internal_wdt_reset,
  .report = internal_wdt_report,
  .name   = "WDT0",
}

WDT0 block descriptor (self-registered with the core).

Definition at line 217 of file board_periph_wdt.c.

Referenced by internal_wdt_block_register().

◆ s_wdt

wdt_state_t s_wdt

static

Definition at line 87 of file board_periph_wdt.c.

Referenced by internal_wdt_read(), internal_wdt_report(), internal_wdt_reset(), internal_wdt_tick(), and internal_wdt_write().

Data Structures

Enumerations

Functions

Variables

Detailed Description

Enumeration Type Documentation

◆ wdt_field_t

◆ wdt_geom_t

◆ wdt_order_t

Function Documentation

◆ internal_wdt_block_register()

◆ internal_wdt_read()

◆ internal_wdt_report()

◆ internal_wdt_reset()

◆ internal_wdt_tick()

◆ internal_wdt_write()

Variable Documentation

◆ s_k_wdt_block

◆ s_wdt