ISO 20794-4-2020 pdf free download – Road vehicles — Clock extension peripheral interface (CXPI) — Part 4: Data link layer and physical layer.
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 ISO 20794-3, Road vehicles — Clock extension peripheral interface (CXPI) — Part 3: Transport and network layer
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20794-2, ISO 20794-3, and ISO/IEC 7498-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
bit rate
transmission speed (bit/s) of the protocol within the specification range of transmit frames
3.3
higher OSI layer
OSI layer 3 or more than higher number of layers
3.4
idle state
state of the CXPI network when no frames are exchanged (idle state) and only the clock exists to synchronise the nodes
3.5
inter frame space
IFS
time interval between frames on the CXPI network
4 Symbols and abbreviated terms
4.1 Symbols
C BUS total bus capacitance
C LINE capacity of CXPI network
C MASTER capacity of master node
C SLAVE capacity of slave node
kbit/s kilobit per second
LEN BUS length of CXPI bus wire
R BUS total bus-resistor including all slave nodes resistors and master node resistor
R MASTER master node resistor
R SLAVE slave node resistor
t bit bit time
t bit_ref bit time of reference bit rate
t rx_dif_cont difference of the dominant time between logical value ‘1’ and logical value ‘0’
t rx_wakeup_clk time that the receiving clock master detects the width of dominant level as the wake up pulse.
t rx_wakeup time that the receiving node detects each width of dominant level in the wake-up pulse.
t rx_wakeup_space limitation time of acceptance second dominant pulse in the wake-up pulse from first dominant pulse.
t tx_wakeup time that the transceiver node transmits the dominant voltage of the wake-up pulse
t tx_wakeup_space interval time between two of dominant level of transmitting wake-up pulse
t tx_0_lo dominant time of logical value ‘0’
t tx_0_lo_dom dominant time of logical value ‘0’ (TH tx_dom = 30 % of V SUP.ISO 20794-4 pdf download.