Bootloader Addressing

Communicating with the C0-microSD is achieved through block read and write operations. The following specification contains the different address offsets you can use to communicate with the device while in Bootloader mode.

Address space	Address Start	Size	Operation	Description
CONFIGURATION_ID_OFFSET	0x020000	4 Bytes	R	Offset for configuration ID
CONFIGURATION_VERSION_OFFSET	0x020004	4 Bytes	R	Offset for configuration version
CONFIGURATION_STATE_OFFSET	0x020008	4 Bytes	R	Offset for configuration state
BOOTLOADER_SWITCH_CONFIG_OFFSET	0x040000	4 Bytes	W	Offset for switching operation modes
BOOTLOADER_UNLOCK_OFFSET	0x060000	4 Bytes	W	Offset for locking/unlocking bootloader
BOOTLOADER_BITSTREAM_OFFSET*	0x080000	512 KiB	R/W**	Bootloader bitstream region
SIGNALOID_CORE_BITSTREAM_OFFSET*	0x100000	512 KiB	R/W**	Signaloid SoC bitstream region
USER_BITSTREAM_OFFSET*	0x180000	512 KiB	R/W	Custom user bitstream region
USER_DATA_OFFSET*	0x200000	14 MiB	R/W	User data space region

* Address space corresponds to on-board flash memory data.
** Address space needs unlocking for write operation.

CONFIGURATION_ID_OFFSET

This 4-byte word stores the ID of the active configuration (in this case the Bootloader). This is used by the toolkit to identify the active mode of operation of the C0-microSD.

CONFIGURATION_VERSION_OFFSET

This 4-byte word stores the current version of the active configuration (in this case the Bootloader). Specifically:

Active Configuration	Word
Bootloader	b”SBLD”
Signaloid SoC	b”SSOC”

CONFIGURATION_STATE_OFFSET

This 4-byte word stores the current state of the active configuration (in this case the Bootloader). Currently, this is used by the toolkit to verify whether the C0-microSD is in SWITCHING state.

BOOTLOADER_SWITCH_CONFIG_OFFSET

This offset is used for switching between operation modes. To achieve this, you can write the 4-byte word SBLD (ASCII encoded) to this offset.

BOOTLOADER_UNLOCK_OFFSET

Address spaces BOOTLOADER_BITSTREAM_OFFSET and SIGNALOID_CORE_BITSTREAM_OFFSET are locked by default. This is to prevent accidental overriding of the Bootloader or Signaloid SoC bitstreams, which could render the device inoperable. To flash these address spaces, you must first write a special 4-byte word (ASCII encoded UBLD) to this offset. You can re-lock the bootloader by writing anything else to the same offset.

BOOTLOADER_BITSTREAM_OFFSET

In this address space, the Bootloader bitstream is stored. You first need to unlock the bootloader to write to this address space.

SIGNALOID_CORE_BITSTREAM_OFFSET

In this address space, the Signaloid SoC bitstream is stored. You first need to unlock the bootloader to write to this address space.

USER_BITSTREAM_OFFSET

In this address space, the custom user bitstream is stored.

USER_DATA_OFFSET

This 14 MiB address space can be used to store data, or binary files to be used either by the custom user bitstream, or the Signaloid SoC configuration. Specifically, the Signaloid SoC initializes its memory by copying the first 128 KiB section of this address space, before starting its execution.

Important notes

The SD interface mandates the support of read and write operations for the entire available address space. This is in contrast to the supported operation in each address space as described above. For that reason, the following rules apply:

• R: Reading from this address space will return valid data. Writing to this address space will succeed, but will have no effect.
• W: Reading from this address will succeed, but will return invalid data. Writing data to this address space will succeed, and will have an effect on the device.

• R/W: Reading from this address space will return valid data. Writing data to this address space will succeed, and will have an effect on the device.

• N/A: Reading from this address will succeed, but will return invalid data. Writing to this address space will succeed, but will have no effect.

Address spaces that are not mentioned in the table above can be considered as N/A.