ISO 20794-4:2020 pdf download – Road vehicles — Clock extension peripheral interface (CXPI) — Part 4: Data link layer and physical layer.
1 Scope This document specifies the CXPI data link layer and the CXPI physical layer. The DLL is based on: — priority-based CXPI network access; — non-destructive content-based arbitration; — broadcast frame transfer and acceptance filtering; and — node related error detection and error signalling. The CXPI physical layer (PHY) requirements comprise of: — physical signalling (PS) sub-layer, which specifies the requirements of the clock generation function, the encoding and decoding of CXPI frames, and bit-wise collision resolution logic; — physical media attachment (PMA) sub-layer, which specifies the requirements of the signal shaping waveform logic; — physical media dependent (PMD) sub-layer, which specifies the requirements of the CXPI network termination, electrostatic discharge protection, etc., and device connector requirements; and — physical media (PM), which specifies the requirements of the CXPI network cable/wiring harness. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 7498-1, Information technology — Open Systems Interconnection — Basic Reference Model: The Basic Model ISO 20794-2, Road vehicles — Clock extension peripheral interface (CXPI) — Part 2: Application layer
9.1 PHY — Overview The CXPI physical layer (PHY) comprises the physical signalling (PS) sub-layer, which is implemented in the CXPI protocol or the CXPI transceiver or the CXPI System Base Chip (SBC). It also comprises the physical media attachment (PMA) sub-layer, which is implemented normally in the CXPI transceiver or the CXPI SBC, which also may implement additional protection circuitry, not in scope of this document. The CXPI PHY also comprises the physical media dependent (PMD) sub-layer, which includes cable, and the termination resistors. Figure 16 specifies an overview of the PHY sub-layers. The PHY sub-layers are comprises the: — Physical signalling (PS) sub-layer, which specifies the requirements of the clock generation function, the encoding and decoding of CXPI frames, and the bit-wise collision resolution logic. — Physical media attachment (PMA) sub-layer, which specifies the requirements of the signal shaping waveform logic. — Physical media dependent (PMD) sub-layer, which specifies the requirements of the CXPI network termination, electrostatic discharge protection, etc., and device connector requirements. — Physical media (PM), which specifies the requirements of the CXPI network cable/wiring harness.