Pocket Challenge stuff

pocket_challenge.md

Pocket Challenge (JA734) System Config

Nuvoton Stuff

• N32905 BSP
• Linux Port
• Datasheet - Just Google it.

Memory Layout

• 0x00000000 - 0x00100000 - (v) SRAM region mirrored by TLB
  • 0x00000000 - 0x00002000 - SRAM mirror
• 0x80000000 - 0x82000000 - (v, p) 32MiB SDRAM
  • 0x80000000 - 0x81d00000 - OS + BSS (kernel and system heap)
  • 0x81d00000 - 0x82000000 - Reserved area (VRAM, TLB, etc.)
• 0xb0000000 - 0xc0000000 - (v, p) MMIO (see W55FA93_reg.h)
• 0xff000000 - 0xff002000 - (p) 8KiB SRAM (probably inaccessible directly after OS enables MMU)
• 0xffff0000 - 0xffff4000 - (p) BootROM (?, probably inaccessible directly after OS enables MMU)

v - virtual memory (accessible after TLB is enabled), p - physical memory

Bootloader

Stage 0 (boot ROM)

Probably just standard Nuvoton stuff. It'd be great if we can dump it but this is probably not really necessary for a simple emulator (assuming that it doesn't do too much initialization work that the rest of the OS cares about).

Stage 1

Legacy N32905 boot header can be found at the sector 1 of the SD card. The boot header seemingly asks the boot ROM to load 0x10000 bytes to 0x80a00000 (only the first 0x4000 bytes seems to be the actual stage 1 though).

Stage 2

Stage 1 reinitializes the SD card and loads 0x80000 bytes from sector 33 to 0x80c00000. This then loads the kernel from the 1MiB mark on the SD card to 0x80000000 and finally boots it.

Pinctrl

Function Selection

• GPIO: 0b00
• Port A UART1: 0b11
• Port E SD: 0b10

Board Config

Pin	Function	Description
A3	GPIO	VBAT comparator out? (bootloader immediately powers the system off if it's 0)
A10-A11	UART1	UART debug output (bootloader only)
E2-E7	SD0	eSD

Bootloader Poweroff Sequence

RTC_FCR[2:] = 0b10
RTC_PWRON[20:16] = 0b0000
RTC_PWRON[1:] = 0b0
AHBCLK[:] = 0