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 +	ACK / NAK (NOTE: takes 7+n bytes in opbuf)
					 + length bytes of data
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	ACK + rlen bytes of data / NAK
					 + slen bytes of data
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
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_CMD_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.
	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.h.