LIN Network for Vehicle ApplicationsIssued 2004-08Revised 2005-09Superseding J2602-1 AUG2004
SAE J2602-1 Revised SEP2005
5.8.3
SIGNAL ENCODING TYPES (REF. SECTION 1.1, LIN 2.0 PROTOCOL SPECIFICATION)
Since only two signal encoding types are allowed in the LIN 2.0 protocol specification (scalar and byte array), and there is an expectation to employ other standard signal encoding types commonly used in other serial data implementations, the following recognized signal encoding types shall be mapped into the two LIN signal encoding types in accordance with the following table. Appendix B Signal Encoding Types contains descriptions and examples of each of the signal encoding types listed. TABLE 2—COMMON SIGNAL ENCODING TYPE MAPPING TO LIN DEFINED DATA ENTITIESSignal Encoding Type ASCII Slot Type ASC Mapped to LIN Data Type 8-bit Scalar Notes Most Significant Bit reserved and set to“0”, ASCII codes 0 through 127 Must be on nibble boundaries.
Binary Coded Decimal Boolean Enumerated Signed Floating Point Signed Numeric Unsigned Numeric
BCD BLN ENM SFP SNM UNM
4 bit Scalar per BCD character 1 bit Scalar N bit Scalar, in increments of 1 bit (1– 16 bits) 4 byte - Byte Array 8, 16, or 32 bit Byte Array N bit Scalar, increments of 8 bits (1 byte)
As defined in ANSI/IEEE Std 754-1985 2’s Complement notation Not to exceed 16 bits (2 bytes)
Note that slave devices may transmit a maximum of 7 data bytes as the first data byte has been reserved for the J2602 Status Byte. The master device may transmit 8 data bytes, as it is not required to transmit the J2602 Status Byte. (See 5.8.6 J2602 Status Byte.) 5.8.4 SIGNAL MANAGEMENT
Signals may belong to multiple frames, e.g. J2602 Status Byte. Signals may also be placed in the same frame multiple times, e.g. Broadcast messages. 5.8.5 UNUSED BITS IN THE DATA FIELD (REF. SECTION 2.3, LIN 2.0 PROTOCOL SPECIFICATION)
The length of each frame in bytes, used for LIN normal communications (not diagnostics or configuration), shall be defined for each LIN network, on a frame-by-frame basis. Any bits of a defined frame that are either not used or not defined shall be transmitted as recessive symbols. Padding of unused data bytes within LIN normal communications messages is not required. That is, normal communications messages may vary in length between 1 byte and 8 bytes. 5.8.6 J2602 STATUS BYTE
This section defines a single standardized format for a J2602 Status Byte, which encompasses both LIN Protocol Error reporting and application specific information. The J2602 Status Byte contains two enumerated bit fields, a 3 bit error field, and a 5 bit field for application specific information. Only the error field is defined, since it is the only one with the error and status states explicitly defined. The application information field is defined and implemented on a caseby-case basis, dependent on the requirements of each slave no
de application. The resulting application information field implementation is documented in the NCF for each slave node. This status byte shall be transmitted as the first byte of every slave transmission, where the identifier is in the range of$00 through$3B.
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