The VM1602 is a high-performance event monitor with time stamp recording capability. The instrument monitors each of its 32 inputs for an event and records the time when the event occurred. The time is recorded by saving the value of a 40-bit time counter into memory, along with a 32-bit event source value corresponding to the channel or channels which caused the event to occur. An event occurs on a channel when the input has a rising or falling edge. Each channel is independently programmed for rising or falling edge detection. The instrument can collect a total of 128 k events, or 512 k events when the extended memory option is installed.
Each input can be configured for either differential or single-ended operation. In differential mode, a high input occurs when the positive input is at a higher potential than the negative input. In single-ended mode, a high input occurs when the positive input of a channel is at a higher potential than the programmed threshold voltage for the corresponding channel.
The time stamp which is recorded with each input event consists of a 40-bit time counter value. This counter increments at a rate of 1 µs, 10 µs, 100 µs or 1 ms. All time measurements are then made by finding the difference between time counter values multiplied by the increment rate of the counter.