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.
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.
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