PoC.misc.sync offers different clock-domain-crossing (CDC)
synchronizer circuits. All synchronizers are based on the basic 2 flip-flop
synchonizer called sync_Bits. PoC has two
platform specific implementations for Altera and Xilinx, which are choosen,
if the appropriate
MY_DEVICE constant is configured in
|Behavior||Flag ||Strobe ||Continuous Data||Reset ||Pulse |
|1 Bit||sync_Bits||sync_Strobe||fifo_ic_got ||sync_Reset||sync_Pulse|
|n Bit||sync_Vector||sync_Command||fifo_ic_got |
Basic 2 Flip-Flop Synchronizer
The basic 2 flip-flop synchronizer is called sync_Bits. It’s
possible to configure the bit count of indivital bits. If a vector shall be
synchronized, use one of the special synchronizers like sync_Vector. The
vendor specific implementations are named
A second variant of the 2-FF synchronizer is called sync_Reset.
Reset-signals, implementing asynchronous assertion and synchronous
deassertion. The vendor specific implementations are named
A third variant of a 2-FF synchronizer is called sync_Pulse.
It’s for very short
Pulsed-signals. It uses an addition asynchronous capture FF to latch the
very short pulse. The vendor specific implementations are named
Based on the 2-FF synchronizer, several “high-level” synchronizers are build.
- sync_Strobe synchronizer
strobe-signals across clock-domain-boundaries. A busy signal indicates the synchronization status and can be used as a internal gate-signal to disallow new incoming strobes. A
strobe-signal is only for one clock period active.
- sync_Command like
sync_Strobe, it synchronizes a one clock period active signal across the clock-domain-boundary, but the input has multiple bits. After the multi bit strobe (Command) was transfered, the output goes to its idle value.
- sync_Vector synchronizes a complete vector across the clock-domain-boundary. A changed detection on the input vector causes a register to latch the current state. The changed event is transfered to the new clock-domain and triggers a register to store the latched content, but in the new clock domain.
- For a cross-clock capable FIFO.
|||A flag or status signal is a continuous, long time stable signal.|
|||A strobe signal is active for only one cycle.|
|||A pulse signal is a very short event.|
|||To be refumented|
|||(1, 2) See the |