Intel C2518 FH8065501516710 Data Sheet

Intel

®

 Atom™ Processor C2000 Product Family for Microserver

September 2014

Datasheet, Vol. 2 of 3

Order Number: 330061-002US

349

7

Message Control

Bit 7: Start of Message (SOM): Set to 1 if the packet is the start of message.
Bit 6: End of Message (EOM): Set to 1 if the packet is the end of message.
Combinations of SOM, EOM are used to identify the Start, Middle, and End of a 

Message that is split across one or more packets.
Bits [5:4]: Sequence Number: For messages that span multiple packets, this 

field helps identify lost intermediate packets. Increments on each successive 

packet. The value of the Sequence Number for Packet N, is the Packet N-1 

Sequence Number + 1 mod 4.
Bit 3: Initiator (I): Set to 1 if value of Message Tag field was assigned by the 

source (for requests) or set to 0 of the Message Tag was assigned by the 

destination (for responses).
Bits [2:0]: Message Tag (MT): This field, along with the Source Endpoint ID, 

identifies a unique Message ID. The Message ID must be unique for all 

outstanding request transactions that require a response and have not yet receive 

the response. For Response messages, the Message Tag sent with the Request is 

returned in the Response. 

8

Message  Header Begin  MCTP Message Header

M

Message Data

MCTP defined

N

PEC

Single byte Packet Error Check accompanies all MCTP messages.