J1850
SAE J1850 is an automotive communications protocol used mainly for on-board diagnostics (OBD) and in-vehicle networking. Before CAN became standard, it was widely used in vehicles. J1850 lets electronic control units (ECUs) communicate in the vehicle.
Wrong bit order, invert setting, or PWM/VPW timing yields incorrect frames. For channel-prefix differences, see Settings.
Decode Settings
- Channel: J1850 signal channel.
- Bit order: MSB First/LSB First. Default: MSB First.
- Invert waveform: Invert the waveform for analysis. Field enabled (Enable) when checked. Default: cleared.
- Manufacture: Manufacturer (affects NB/CRC behavior). Field enabled (Enable) only when Transfer Method is VPW; field disabled (Disable) for PWM. Currently GM and Chrysler; contact us for more options. Default is not reset by the Default button.
- Transfer Method: PWM or VPW (different timing groups; editable). PWM enables (Enable) the PWM timing group and disables (Disable) VPW timing plus Manufacture/NB color; VPW does the opposite. Default: VPW.
- PWM timing (µs): Field enabled (Enable) when Transfer Method is PWM. Parameters and Defaults:
- Active Phase "1": Active pulse width for logic 1. Default: 8 µs.
- Active Phase "0": Active pulse width for logic 0. Default: 16 µs.
- Bit Time: Full bit period. Default: 24 µs.
- SOF/EOD Time: Start of Frame/End of Data duration. Default: 48 µs.
- EOF Time: End of Frame duration. Default: 72 µs.
- IFS Time: Inter-Frame Separation. Default: 96 µs.
- Active SOF: Active pulse width of SOF. Default: 32 µs.
- Active BRK: Active pulse width of Break. Default: 40 µs.
- BRK to IFS Time: Time from Break end to IFS. Default: 120 µs.
- VPW timing (µs): Field enabled (Enable) when Transfer Method is VPW. Default: Short Pulse 64, Long Pulse 128, SOF/EOD Time 200, EOF Time 280, BRK Time 300, IFS Time 300.
Result
PWM:
VPW:
