FPGA Wisdom from Adam Taylor Counters
Adam Taylor latest article on EE Times cover ten ways to create reliable FPGA designs is a great read.
Number 7
There are a number of techniques we can use to ensure the designs we implement within our FPGAs are capable of operating reliably.
Counters
Adam Taylor writes
‘Within our FPGA, we will use counters for a variety of purposes. We may want them to record the time between events or use them to generate periodic actions. Often, we will use counters in conjunction with state machines.’
FPGA counter use for safe reliable operation
(Source: Adam Taylor)
‘Most counters will not count to a power of two. As such, there are values above the terminal count. Should the registers holding the count value become corrupted, the value stored could be above the terminal count value. Such an error could lead to incorrect operation of the FPGA function or cause it to completely lock up. One way we can protect against such an occurrence is to use the greater-than-or-equal-to operator as opposed to the equal-to operator as illustrated above.’
Never happens?
For those of you who think that this can never happen I have seen this exact issue happen in FPGA developments.
Adam Taylor’s article
The complete article with all ten techniques is available here.