SRL::Tickstamp Class Reference

Detailed Description

High-precision 48-bit timestamp with DVU hardware acceleration.

Stores timer values as a 48-bit composite (32-bit overflow counter + 16-bit FRT). The internal representation uses 64-bit storage (high=Timer32, low=FRT<<16) to enable hardware-accelerated division via the SH-2 DVU.

Architecture & PHI_128 Mode:

This class is designed specifically for the Sega Saturn's FRT (Free Running Timer) running in PHI_128 mode (~222 kHz, ~4.47μs precision). This matches SGL's default FRT configuration. Changing the FRT clock mode after initialization will break all timing calculations.

• FRT (Free Running Timer): 16-bit hardware counter at PHI_128 (~222 kHz)
• timer32: 32-bit overflow counter incremented each time FRT wraps (~295ms)
• 48-bit total range: 0 to 2^48-1 ticks (~673 days at PHI_128)

Divider Strategy:

The DVU performs 64-bit / 32-bit division: (ticks << 16) / divisor where divisor = frequency / 128, matching the PHI_128 tick rate directly. This gives correct Fxp 16.16 results without any tick normalization shifts.

Example: 1 second at 26.6875 MHz

• Ticks = 26,687,500 / 128 = 208,496
• Dividend = 208,496 << 16 = 13,667,041,280
• Divisor = 26,687,500 / 128 = 208,496
• Result = 65,536 = 1.0 in Fxp 16.16 ✓

Fxp Conversion Limits:

While the Tickstamp can store up to ~673 days, conversion functions return Fxp (16.16 format) which has a hard limit of 32767 in the integer part:

• ToMilliseconds(): Maximum ~32767 ms (~32.8 seconds)
• ToSeconds(): Maximum ~32767 seconds (~9.1 hours)
• ToMinutes(): Maximum ~32767 minutes (~22.7 days)
• ToClock(): Maximum ~546 hours (~22.7 days), returns ClockTime struct For durations exceeding Fxp limits, use ToClock() which returns individual components.

Usage Example:

Tickstamp start = Timer::Capture();          // Capture start time
// ... do some work ...
Tickstamp end = Timer::Capture();            // Capture end time
Tickstamp elapsed = end - start;             // Calculate elapsed (64-bit subtraction)
Fxp seconds = elapsed.ToSeconds();           // Convert to seconds (Fxp 16.16)

Warning

This class assumes FRT is configured in PHI_128 mode (SGL default). Behavior is undefined if the FRT clock mode is changed after initialization.

#include <srl_timer.hpp>

Classes
struct	ClockTime
	Immutable clock display format (HH:MM:SS.mmm). More...

Public Member Functions
	Tickstamp ()=default
	Default constructor. Initializes to zero.
Core Operations
Essential timer operations for time calculations.
Tickstamp	operator- (const Tickstamp &other) const noexcept
	64-bit subtraction with borrow (hardware-accelerated).
Tickstamp	operator+ (const Tickstamp &other) const noexcept
	64-bit addition with carry (hardware-accelerated).
bool	operator== (const Tickstamp &other) const noexcept
	Equality comparison.
bool	operator!= (const Tickstamp &other) const noexcept
	Inequality comparison.
bool	operator< (const Tickstamp &other) const noexcept
	Less-than comparison.
bool	operator> (const Tickstamp &other) const noexcept
	Greater-than comparison.
bool	operator<= (const Tickstamp &other) const noexcept
	Less-than-or-equal comparison.
bool	operator>= (const Tickstamp &other) const noexcept
	Greater-than-or-equal comparison.
Math::Types::Fxp	ToMilliseconds () const noexcept
	Converts ticks to milliseconds using DVU hardware acceleration.
Math::Types::Fxp	ToSeconds () const noexcept
	Converts ticks to seconds using DVU hardware acceleration.
Math::Types::Fxp	ToMinutes () const noexcept
	Converts ticks to minutes using DVU hardware acceleration.
ClockTime	ToClock () const noexcept
	Converts ticks to clock display format (HH:MM:SS.mmm) using 1 DVU division.

Static Public Member Functions
Compile-Time Builders
Create Tickstamps at compile time with no runtime conversion overhead. These builders calculate both 26MHz and 28MHz tick counts at compile time, storing two complete Tickstamps, then return a reference to the appropriate one at runtime based on the active divider.
static constexpr Tickstamp	FromTicks (uint64_t ticks)
	Create Tickstamp from raw tick count at compile time.
template<float Seconds>
static const Tickstamp &	FromSeconds ()
	Create Tickstamp from seconds at compile time (dual-frequency).
template<float Milliseconds>
static const Tickstamp &	FromMilliseconds ()
	Create Tickstamp from milliseconds at compile time (dual-frequency).
template<float Minutes>
static const Tickstamp &	FromMinutes ()
	Create Tickstamp from minutes at compile time (dual-frequency).

Public Attributes
uint32_t	High
	High 32 bits of the 48-bit timestamp.
uint32_t	Low
	Low 32 bits formatted for DVU division.