California Code of Regulations › Title 21 - Public Works › Division 2 - Department of Transportation › Chapter 16 - Compatibility Specifications for Automatic Vehicle Identification Equipment › Article 3 - Introduction › Section 1702.2 - Definitions for Data Codes

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
(a) Agency
				  Code: This 16-bit code field identifies the agency that has authority to
				  conduct the transaction.
(b) Byte
				  Order: Numeric fields shall be transmitted by the most significant bit first.
				  If a numeric field is represented as multiple bytes, the most significant bit
				  of the most significant byte is transmitted first. This document represents the
				  most significant and first transmitted to the left on a line and to the top of
				  a multi line tabulation.
(c) Error
				  Detection Code: The error detection code utilized in the defined records is the
				  CRC-CCITT, with a generator polynomial of
				  X16+X12+X5+1.
				  This results in a 16-bit BCC transmitted with each data message. The data field
				  protected by the CRC excludes any preceding header in every case.
(d) Filler Bits: Filler bits are used to
				  adjust the data message length to a desired length and shall be set to
				  zero.
(e) Header Code: The header
				  is the first field in each data message for either reader or transponder
				  transmissions and consists of an 8-bit and a 4-bit word for a total of 12 bits.
				  The header provides a signal that may be used by a receiver to self-synchronize
				  (selsyn) with the data being transmitted, thus the notation selsyn. The selsyn
				  signal has binary and hexadecimal values: 10101010 and AA, respectively.
The header code also provides for a unique, 4 bit flag that
					 is recognized by a receiver decoder as the end of the header with the data
					 message to follow. The flag signal has binary and hexadecimal values: 1100 and
					 C respectively.
(f) Reader
				  ID Number: This 32-bit field is used to uniquely identify the reader conducting
				  the transaction.
(g) Transaction
				  Record Type Code: This 16-bit code uniquely identified a specific type of valid
				  transaction between a reader and a transponder. This code uniquely defines the
				  transponder message fields and functions permissible with the transaction type
				  specified by the polling message as described in Section
				  1703.5(e)(1).
				  Hexadecimal numbers 1 through 7FFF are set aside for transponder message
				  structures and 8000 through FFFF are dedicated for reader-to-transponder
				  message structures.
(h) Transaction
				  Status Code: Used to provide status information to the transponder.
(i) Transponder ID Number: This 32-bit code
				  uniquely identifies which transponder is responding to a polling request or is
				  being acknowledged.
1. New
					 section filed 6-26-92; operative 7-27-92 (Register 92, No. 26).
2.
					 Repealer of former section
					 1702.2 and renumbering of former
					 section 1703 to new section
					 1702.2, including amendment of
					 subsections (b) and (g), filed 11-28-2017; operative 1-1-2018 (Register 2017,
					 No. 48).
Note: Authority cited: Section
						27565,
						Streets and Highways Code. Reference: Sections
						27564
						and
						27565,
						Streets and Highways Code.