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SAE J2735-Draft-Rev28 [issued: 11-10-08]
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154 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
<xs:documentation>
edit to proper ranges. add predefined values
</xs:documentation>
</xs:annotation>
<xs:restriction base="xs:unsignedShort">
<xs:maxInclusive value="65000"/>
</xs:restriction>
</xs:simpleType>
Used By: This entry is used directly by one other data structure in this standard, a DF called
MSG_TravelerInformation <ASN> <XML>. In addition, this item may be used by data structures in
other ITS standards.
7.87 Data Element: DE_MsgCount
Use: The DE_MsgCount data element is used (typically as the 2nd payload word of each message) to
provide a sequence number for all messages of the same type. Sequential messages of the same type (and
from the same sending device) are expected to have sequential numbering advancing by one with each new
message (regardless of the number of applications that may be involved in the creation or use). The receipt
of a non-sequential number implies that a stream of messages from that sending device has been lost. Note
that the sequence is tied to each message type, not the application, nor the device. The value rolls over
from 127 to zero. The value send may restart any time the device has not transmitted a messages of that
type for more than 10 seconds.
ASN.1 Representation:
MsgCount ::= INTEGER (0..127)
XML Representation:
<xs:simpleType name="MsgCount" >
<xs:restriction base="xs:unsignedByte">
<xs:maxInclusive value="127"/>
</xs:restriction>
</xs:simpleType>
Used By: This entry is directly used by the following 8 other data structures in this standard (record type,
descriptive name, ASN.1, and XML name (if present) of each):
MSG
<XML>, and
MSG
<XML>, and
DF
<XML>, and
MSG
<XML>, and
MSG
<XML>, and
MSG
<XML>, and
MSG
<XML>, and
DF
In addition, this item may be used by data structures in other ITS standards.
7.88 Data Element: DE_MsgCRC
Use: A two byte data element calculated over the payload bytes of the message (starting with the initial
sequence and ending with the last data element before the CRC itself and including all tag, length, and
values bytes found in between). Typically placed as the every last data element in the message. The
generating polynomial used is the "CRC-CCITT" commonly expressed as x^16 + x^12 + x^5 + 1. An
initial seed value of zero shall be used. Note that because the first byte of every DSRC message is never