Abstract: The subject matter of this specification can be embodied in, among other things, an internal combustion engine ignition system includes a voltage divider configured to be coupled to a primary transformer ignition coil connector, the voltage divider configured to reduce a voltage received from the primary transformer ignition coil to a controller voltage, a comparator circuit with an input coupled to an output of the voltage divider, and a controller configured to detect the voltage output of the voltage divider, detect the voltage output of a vehicle electric power supply, detect the voltage output of a comparator, and determine an estimated breakdown voltage of a spark plug based on the detected output voltage of the voltage divider and the detected voltage of the power supply.

Abstract: A method and apparatus for generating an error detection code, such as a Cyclic Redundancy Checksum (CRC), for a modified binary data block. The modified data block, such as a VLAN frame, is derived from an original binary data block, such as an ethernet frame, having a first error detection code associated therewith. In one embodiment, the method requires modifying the original data block utilizing first data, in the form of VLAN header information, to generate the VLAN frame, whereafter a second error detection code is calculated exclusively for the VLAN header information. More specifically, where the original data block is modified by the insertion of the VLAN header information into the original data block, a CRC is calculated using the VLAN header information shifted to a position corresponding to its position within the modified data block.