18 KiB
- Protocol
- Supported commands
- Asynchronous packets
Protocol
SC64 exposes itself in the system as a simple serial device. This allows it to work without manually installed drivers. Serial communication is also well supported in almost all programming languages making it easy to work with. USB protocol use simple packet based communication. Every packet starts with 3 byte identifier and 1 byte data ID. Every argument/data is sent as big-endian value.
Resetting communication
Due to serial communication nature, data transfer between PC and flashcart might get out of sync (for example when long data transfer is aborted before sending/receiving all bytes).
Communication reset is done via emulated DTR/DSR pins.
Start reset procedure by setting DTR pin value to high (1).
Next, observe DSR pin until its state is set to high (1).
At this point communication has been reset and USB interface is disabled. Now it is a good moment to clear/purge any buffers.
Finish reset procedure by setting DTR pin value to low (0) and observe DSR pin until its state is set to low (0).
Flashcart should be ready to accept new commands.
PC -> SC64 packets
| identifier | description |
|---|---|
CMD |
Send command to the SC64 |
SC64 understands only one packet identifier - CMD.
Fourth byte denotes command ID listed in supported commands section.
CMD packet
General structure of packet:
| offset | type | description |
|---|---|---|
0 |
char[3] | CMD identifier |
3 |
char[1] | Command ID |
4 |
uint32_t | First argument (arg0) |
8 |
uint32_t | Second argument (arg1) |
12 |
uint8_t[data_length] | Command data (if required) |
CMD packet always require arguments to be sent even if command does not require them.
Packet data length is derived from the argument if specific command supports it.
SC64 -> PC packets
| identifier | description |
|---|---|
RSP |
Success response to the received command |
ERR |
Error response to the received command |
PKT |
Asynchronous data packet |
SC64 sends response packet RSP/ERR to almost every command received from the PC.
Fourth byte is the same as in the command that triggered the response.
If command execution was not successful, then RSP identifier is replaced by the ERR identifier.
SC64 can also send PKT packet at any time as a response to action triggered by the N64 or the flashcart itself.
Fourth byte denotes packet ID listed in the asynchronous packets section.
RSP/ERR packets
General structure of packet:
| offset | type | description |
|---|---|---|
0 |
char[3] | RSP/ERR identifier |
3 |
char[1] | Command ID |
4 |
uint32_t | Data length |
8 |
uint8_t[data_length] | Response data (if any) |
RSP/ERR packet is sent as a response to the command sent by the PC.
ERR response might contain no (or undefined) data in the arbitrary data field compared to regular RSP packet.
PKT packet
General structure of packet:
| offset | type | description |
|---|---|---|
0 |
char[3] | PKT identifier |
3 |
char[1] | Packet ID |
4 |
uint32_t | Data length |
8 |
uint8_t[data_length] | Packet data (if any) |
Available packet IDs are listed in the asynchronous packets section.
Supported commands
| id | name | arg0 | arg1 | data | response | description |
|---|---|---|---|---|---|---|
v |
IDENTIFIER_GET | --- | --- | --- | identifier | Get flashcart identifier SCv2 |
V |
VERSION_GET | --- | --- | --- | version | Get flashcart firmware version |
R |
STATE_RESET | --- | --- | --- | --- | Reset flashcart state (CIC params and config options) |
B |
CIC_PARAMS_SET | cic_params_0 | cic_params_1 | --- | --- | Set CIC emulation parameters (disable/seed/checksum) |
c |
CONFIG_GET | config_id | --- | --- | config_value | Get config option |
C |
CONFIG_SET | config_id | config_value | --- | --- | Set config option |
a |
SETTING_GET | setting_id | --- | --- | setting_value | Get persistent setting option |
A |
SETTING_SET | setting_id | setting_value | --- | --- | Set persistent setting option |
t |
TIME_GET | --- | --- | --- | time | Get current RTC value |
T |
TIME_SET | time_0 | time_1 | --- | --- | Set new RTC value |
m |
MEMORY_READ | address | length | --- | data | Read data from specified memory address |
M |
MEMORY_WRITE | address | length | data | --- | Write data to specified memory address |
U |
USB_WRITE | type | length | data | N/A | Send data to be received by app running on N64 (no response!) |
D |
DD_SET_BLOCK_READY | success | --- | --- | --- | Notify flashcart about 64DD block readiness |
W |
WRITEBACK_ENABLE | --- | --- | --- | --- | Enable save writeback through USB packet |
p |
FLASH_WAIT_BUSY | wait | --- | --- | erase_block_size | Wait until flash ready / Get flash block erase size |
P |
FLASH_ERASE_BLOCK | address | --- | --- | --- | Start flash block erase |
f |
FIRMWARE_BACKUP | address | --- | --- | status/length | Backup firmware to specified memory address |
F |
FIRMWARE_UPDATE | address | length | --- | status | Update firmware from specified memory address |
? |
DEBUG_GET | --- | --- | --- | debug_data | Get internal FPGA debug info |
% |
STACK_USAGE_GET | --- | --- | --- | stack_usage | Get per task stack usage |
v: IDENTIFIER_GET
Get flashcart identifier SCv2
This command does not require arguments or data.
response (identifier)
| offset | type | description |
|---|---|---|
0 |
char[4] | Identifier |
Identifier is always SCv2 represented in ASCII code.
V: VERSION_GET
Get flashcart firmware version
This command does not require arguments or data.
response (version)
| offset | type | description |
|---|---|---|
0 |
uint16_t | Major version |
2 |
uint16_t | Minor version |
4 |
uint32_t | Revision |
Increment in major version represents breaking API changes.
Increment in minor version represents non breaking API changes.
Increment in revision field represents no API changes, usually it's denoting bugfixes.
R: STATE_RESET
Reset flashcart state (CIC params and config options)
This command does not require arguments or data.
This command does not send response data.
This command is used to reset most of the config options to default state (same as on power-up). Additionally, CIC emulation is enabled and 6102/7101 seed/checksum values are set.
B: CIC_PARAMS_SET
Set CIC emulation parameters (disable/seed/checksum)
arg0 (cic_params_0)
| bits | description |
|---|---|
[32:25] |
Unused |
[24] |
Disable CIC |
[23:16] |
CIC seed (IPL2 and IPL3 stages) |
[15:0] |
Checksum (upper 16 bits) |
arg1 (cic_params_1)
| bits | description |
|---|---|
[31:0] |
Checksum (lower 32 bits) |
This command does not send response data.
Use this command to set custom seed/checksum CIC values. Very useful for testing custom IPL3 replacements.
c: CONFIG_GET
Get config option
arg0 (config_id)
| bits | description |
|---|---|
[31:0] |
Config ID |
response (config_value)
| offset | type | description |
|---|---|---|
0 |
uint32_t | Config value |
Use this command to get value of config option. Available config options are listed here.
C: CONFIG_SET
Set config option
arg0 (config_id)
| bits | description |
|---|---|
[31:0] |
Config ID |
arg1 (config_value)
| bits | description |
|---|---|
[31:0] |
Config value |
Use this command to set value of config option. Available config options are listed here.
a: SETTING_GET
Get persistent setting option
arg0 (setting_id)
| bits | description |
|---|---|
[31:0] |
Setting ID |
response (setting_value)
| offset | type | description |
|---|---|---|
0 |
uint32_t | Setting value |
Use this command to get value of persistent setting option. Available persistent setting options are listed here.
A: SETTING_SET
Set persistent setting option
arg0 (setting_id)
| bits | description |
|---|---|
[31:0] |
Setting ID |
arg1 (setting_value)
| bits | description |
|---|---|
[31:0] |
Setting value |
Use this command to set value of persistent setting option. Available persistent setting options are listed here.
t: TIME_GET
Get current RTC value
This command does not require arguments or data.
response (time)
| offset | type | description |
|---|---|---|
0 |
uint8_t | Weekday (1 - 7), 1 represents Monday |
1 |
uint8_t | Hours (0 - 23) |
2 |
uint8_t | Minutes (0 - 59) |
3 |
uint8_t | Seconds (0 - 59) |
4 |
uint8_t | Unused (returns zero) |
5 |
uint8_t | Year (0 - 99) |
6 |
uint8_t | Month (1 - 12) |
7 |
uint8_t | Day (1 - 31) |
Date/time values use the BCD format.
T: TIME_SET
Set new RTC value
arg0 (time_0)
| bits | description |
|---|---|
[31:24] |
Weekday (1 - 7), 1 represents Monday |
[23:16] |
Hours (0 - 23) |
[15:8] |
Minutes (0 - 59) |
[7:0] |
Seconds (0 - 59) |
arg1 (time_1)
| bits | description |
|---|---|
[31:24] |
Unused |
[23:16] |
Year (0 - 99) |
[15:8] |
Month (1 - 12) |
[7:0] |
Day (1 - 31) |
This command does not send response data.
Date/time values use the BCD format.
m: MEMORY_READ
Read data from specified memory address
arg0 (address)
| bits | description |
|---|---|
[31:0] |
Starting memory address |
arg1 (length)
| bits | description |
|---|---|
[31:0] |
Number of bytes to read from the memory |
response (data)
| offset | type | description |
|---|---|---|
0 |
uint8_t[length] | Memory contents |
Reads bytes from the specified memory address. Please refer to the internal memory map for available memory ranges.
M: MEMORY_WRITE
Write data to specified memory address
arg0 (address)
| bits | description |
|---|---|
[31:0] |
Starting memory address |
arg1 (length)
| bits | description |
|---|---|
[31:0] |
Number of bytes to write to the memory |
data (data)
| offset | type | description |
|---|---|---|
0 |
uint8_t[length] | Data to write to the memory |
This command does not send response data.
Writes bytes to the specified memory address. Please refer to the internal memory map for available memory ranges.
U: USB_WRITE
Send data to be received by app running on N64 (no response!)
arg0 (type)
| bits | description |
|---|---|
[31:8] |
Unused |
[7:0] |
Datatype |
arg1 (length)
| bits | description |
|---|---|
[31:0] |
Data length |
data (data)
| offset | type | description |
|---|---|---|
0 |
uint8_t[length] | Arbitrary data |
This command does not send response data.
This command does not send RSP/ERR packet response!
This command notifies N64 that data is waiting to be acknowledged.
If N64 side doesn't acknowledge data via m USB_READ N64 command within 1 second then data is flushed and G DATA_FLUSHED asynchronous packet is sent to the PC.
If N64 acknowledge the request, then data is written to the flashcart memory to address specified in m USB_READ N64 command.
Asynchronous packets
| id | name | data | description |
|---|---|---|---|
B |
BUTTON | --- | Button on the back of the SC64 was pressed |
G |
DATA_FLUSHED | --- | Data from USB_WRITE command was discarded |
U |
DEBUG_DATA | debug_data | Data sent from the N64 |
D |
DISK_REQUEST | disk_info/block_data | 64DD disk block R/W request |
I |
IS_VIEWER_64 | text | IS-Viewer 64 printf text |
S |
SAVE_WRITEBACK | save_contents | Flushed save data |
F |
UPDATE_STATUS | progress | Firmware update progress |