# Serial Flasher Protocol Specification

## Version 1 (0x01 return value == 1)

Command And Answer Sequence - all commands give an answer.

PC: COMMAND(8bit) <parameters determined by opcode>

DEV: ACK/NAK(8bit) <OPTIONAL RETURN BYTES (only if ACK)> / nothing

Command 0x10 (SYNCNOP) has a special return of NAK+ACK for synchronization.

ACK = 0x06

NAK = 0x15

All multibyte values are little-endian. Addresses and lengths are 24-bit.

COMMAND | Description | Parameters | Return Value
--- | --- | --- | ---
0x00 | NOP | none | ACK
0x01 | Query programmer iface version | none | ACK + 16bit version (nonzero)
0x02 | Query supported commands bitmap | none | ACK + 32 bytes (256 bits) of supported cmds flags
0x03 | Query programmer name | none | ACK + 16 bytes string (null padding) / NAK
0x04 | Query serial buffer size | none | ACK + 16bit size / NAK
0x05 | Query supported bustypes | none | ACK + 8-bit flags (as per flashrom) / NAK
0x06 | Query connected address lines | none | ACK + 8bit line count / NAK
0x07 | Query operation buffer size | none | ACK + 16bit size / NAK
0x08 | Query maximum write-n length | none | ACK + 24bit length (0==2^24) / NAK
0x09 | Read byte | 24-bit addr | ACK + BYTE / NAK
0x0A | Read n bytes | 24-bit addr + 24-bit length | ACK + length bytes / NAK
0x0B | Initialize operation buffer | none | ACK / NAK
0x0C | Write to opbuf: Write byte | 24-bit addr + 8-bit byte | ACK / NAK (NOTE: takes 5 bytes in opbuf)
0x0D | Write to opbuf: Write n | 24-bit length + 24-bit addr + length bytes of data | ACK / NAK (NOTE: takes 7+n bytes in opbuf)
0x0E | Write to opbuf: delay | 32-bit usecs | ACK / NAK (NOTE: takes 5 bytes in opbuf)
0x0F | Execute operation buffer | none | ACK / NAK
0x10 | Sync NOP | none | NAK + ACK (for synchronization)
0x11 | Query maximum read-n length | none | ACK + 24-bit length (0==2^24) / NAK
0x12 | Set used bustype | 8-bit flags (as with 0x05) | ACK / NAK
0x13 | Perform SPI operation | 24-bit slen + 24-bit rlen + slen bytes of data | ACK + rlen bytes of data / NAK
0x14 | Set SPI clock frequency in Hz | 32-bit requested frequency | ACK + 32-bit set frequency / NAK
0x15 | Toggle flash chip pin drivers | 8-bit (0 disable, else enable) | ACK / NAK
0x16 | Set SPI Chip Select | 8-bit | ACK / NAK
0x17 | Set SPI Mode | 8-bit | ACK / NAK
0x18 | Set CS Mode | 8-bit | ACK / NAK
0x?? | unimplemented command - invalid |  |

Additional information of the above commands:

> About unimplemented commands / startup sequence:

>   Only commands allowed to be used without checking anything are 0x00,0x10 and 0x01 (NOP,SYNCNOP,Q_IFACE). If 0x01 doesn't return 1, dont do anything if you dont support a newer protocol. Then, check support for any other opcode (except 0x02) by using 0x02 (Q_CMDMAP).

> 0x02 (Q_CMDMAP):

>   The map's bits are mapped as follows: cmd 0 support: byte 0 bit 0 cmd 1 support: byte 0 bit 1 cmd 7 support: byte 0 bit 7 cmd 8 support: byte 1 bit 0, and so on.

> 0x04 (Q_SERBUF):

>   If the programmer has a guaranteed working flow control, it should return a big bogus value - eg 0xFFFF.

> 0x05 (Q_BUSTYPE):

>   The bit's are defined as follows: bit 0: PARALLEL, bit 1: LPC, bit 2: FWH, bit 3: SPI.

> 0x06 (Q_CHIPSIZE):

>   Only applicable to parallel programmers. An LPC/FWH/SPI-programmer can report this as not supported in the command bitmap.

> 0x08 (Q_WRNMAXLEN):

>   If a programmer reports a bigger maximum write-n length than the serial buffer size, it is assumed that the programmer can process the data fast enough to take in the reported maximum write-n without problems.

> 0x0F (O_EXEC):

>   Execute operation buffer will also clear it, regardless of the return value.

> 0x11 (Q_RDNMAXLEN):

>   If this command is not supported, assume return of 0 (2^24).

> 0x12 (S_BUSTYPE):

>   Set's the used bustype if the programmer can support more than one flash protocol. Sending a byte with more than 1 bit set will make the programmer decide among them on it's own. Bit values as with Q_BUSTYPE.

> 0x13 (O_SPIOP):

>   Send and receive bytes via SPI. Maximum slen is Q_WRNMAXLEN in case Q_BUSTYPE returns SPI only or S_BUSTYPE was used to set SPI exclusively before. Same for rlen and Q_RDNMAXLEN. This operation is immediate, meaning it doesn't use the operation buffer.

> 0x14 (S_SPI_FREQ):

>   Set the SPI clock frequency. The 32-bit value indicates the requested frequency in Hertz. Value 0 is reserved and should be NAKed by the programmer. The requested frequency should be mapped by the programmer software to a supported frequency lower than the one requested. If there is no lower frequency available the lowest possible should be used. The value chosen is sent back in the reply with an ACK.

> 0x15 (S_PIN_STATE):

>   Sets the state of the pin drivers connected to the flash chip. Disabling them allows other devices (e.g. a mainboard's chipset) to access the chip. This way the serprog controller can remain attached to the flash chip even when the board is running. The user is responsible to NOT connect VCC and other permanently externally driven signals to the programmer as needed. If the value is 0, then the drivers should be disabled, otherwise they should be enabled.

> 0x16 (S_SPI_CS):

>   Set which SPI Chip Select pin to use. This operation is immediate, meaning it doesn't use the operation buffer.

> 0x17 (S_SPI_MODE):

>   Set which SPI Mode to use for 0x13 O_SPIOP commands. This operation is immediate, meaning it doesn't use the operation buffer. The current defined modes are:

>   > - 0x00: SPI Half Duplex (default)

>   > - 0x01: SPI Full Duplex

> 0x18 (S_CS_MODE):

>   Set which CS Mode to use. The CS Mode determines the CS behaviour. This allows manual control over the CS. This operation is immediate, meaning it doesn't use the operation buffer. The current defined modes are:

>   > - 0x00: CS Auto Mode. The CS gets selected before 0x13 O_SPIOP commands and deselected afterwards. (default)

>   > - 0x01: CS Selected. The CS will be selected until another mode is set.

>   > - 0x02: CS Deselected. The CS will be deselected until another mode is set.

> About mandatory commands:

>   The only truly mandatory commands for any device are 0x00, 0x01, 0x02 and 0x10, but one can't really do anything with these commands. Support for the following commands is necessary for flashrom to operate properly: S_CMD_Q_SERBUF, S_CMD_Q_OPBUF, S_CMD_Q_WRNMAXLEN, S_CMD_R_BYTE, S_CMD_R_NBYTES, S_CMD_O_INIT, S_CMD_O_WRITEB, S_CMD_O_WRITEN, S_CMD_O_DELAY, S_CMD_O_EXEC. In addition, support for these commands is recommended: S_CMD_Q_PGMNAME, S_CMD_Q_BUSTYPE, S_CMD_Q_CHIPSIZE (if parallel).

See also `serprog.c`