| 摘要 |
<p>A bus loading meter for a controller area network (CAN) comprises a CAN transceiver (10) which converts an incoming CAN signal to a standard digital (TTL) signal. A counter (20) is provided for capturing the start-of-frame (SOF) and end-of-frame (EOF) of the signal by calculating the number of recessive bits present before a dominant bit (to determine the SOF) and after a dominant bit (to determine the acknowledgement slot) which is followed by seven successive recessive bits indicating the EOF. The meter further comprises a message frame converter (30) which is triggered by receipt of a start pulse from the counter (20) to start counting. Such counting is subsequently terminated on receipt of an end pulse from the counter (20) which resets the converter (30). A message envelope is formed at the output of the converter (30) which is supplied to a volt meter (40) providing a visual indication of the percentage bus loading. The converter (30) is controlled by a frequency switch (32) supplied by a crystal oscillator.</p> |
