Clocks, timers, DMA, watchdog, and power

System clocks

The SoC can run from a 12 MHz source, the 32.768 kHz source, or a PLL-derived clock with a divider. Emulator2 integrates CPU cycles using live clock settings rather than assuming a fixed instruction rate.

Instruction timing is approximate by opcode class. Hardware-visible deadlines for timers, RTC, watchdog, ADC, video, USB suspend, and SPU beat events are scheduled at emulated cycle boundaries.

Timers and interrupts

Four general timers, timebases, RTC scheduling, and multiple interrupt status/ priority banks are modeled. Status fields commonly require write-one-to-clear acknowledgment. A handler must clear both the peripheral source and any aggregate status required by the documented path.

Exact behavior of every counter selector and priority combination remains incomplete; prefer resident timing unless a low-level port needs a tested timer.

System DMA

Four channels copy 16-bit words between CPU/DMA-visible addresses. The SDK provides start, bounded wait, copy, and fill operations. Word count zero, invalid channels/modes, unaligned destinations, and overflowing ranges are rejected. Fixed-source mode validates one source word and the full destination range; incrementing copy validates both ranges.

The wait helper services the watchdog and acknowledges completion. Use a timeout appropriate to the transfer rather than an unbounded busy loop.

Watchdog

The loader can hand off with the watchdog active. A low-level loop must call mg_sdk_watchdog_kick() frequently. Repeated resets every few seconds are a strong sign that the watchdog was inherited but not serviced.

Normal resident applications should not reconfigure watchdog control registers.

Power and sleep

The resident owns the standard Off presentation and terminal power request. Use standard_controls.h in resident applications or direct_controls.h in a framebuffer-owned loop. The direct layer performs the terminal request without an overlay. Raw sleep/power registers and boot wake behavior are not a substitute for the application shutdown contract.

Power-off and application handoff are terminal state transitions; test them last and record their physical evidence separately.