Parameter

Value

Comment

eSPI Cycle Type

21h

OOB Message

Tag[3:0]

0h

Ignored

Length[11:8]

0h

Length[7:0]

Command dependent

Destination/Source Slave Address[7:1]

08h for Intel PCH/ME OOB MCTP Handler

07h for eSPI Slave/EC

Intel ME OOB MCTP Handler address[7:0]=10h(Dest)/11h(Src)

eSPI/EC Address[7:0]=0Eh(Dest)/0Fh(Src)

SMB Command Code

0Fh

0Fh for MCTP over SMBus messages. Ref[5]

Byte Count

Command dependent

Header Version

1h

Ref[5]

Destination Endpoint ID

CSME: 0x50; EC: 0x40

EID (Endpoint identifier) for the endpoint to receive MCTP packet.

Source Endpoint ID

CSME: 0x50; EC: 0x40

EID of the originator of MCTP packet.

SOM (Start of Message flag)

0b/1b

Set to 1b if this packet is the first packet of a message. Ref[4]

EOM (End of Message flag)

0b/1b

Set to 1b if this packet is the last packet of a message. Ref[4]

Packet Seq # (Packet sequence number)

00b/01b

00b for messages that do not span multiple packets. Ref[4]

TO (Tag Owner)

1b

Set to 1b to indicate that the source of the message originated the message tag. Ref[4]

Message Tag

0

Message tag (along with the Source Endpoint IDs and TO field) identifies a unique message at the MCTP transport level

IC (Integrity Check bit)

0b

0b = No MCTP message integrity check. Ref[4]

Message Type

7Dh

Message Type to be requested from DMTF

RPMC Device

00h-03h

Up to four devices including EC as RPMC device and SPI flash devices

MCTP Message Payload

Command dependent

Includes the following:

IC/Message Type byte

RPMC Device

RPMC packet payload