The following tables document the netlist topologies and clock manager settings
for DPLL. The key difference between MMCM and XPLL and DPLL is that DPLL has only
one set of PD and the digital deskew mode requires that CLKIN is connected to
CLKIN_DESKEW. In addition, CLKIN to CLKOUTx cannot be safely timed when
CLKOUTx_PHASE_CTRL = 00 or 10 and CLKOUTx to CLKOUTy cannot be safely timed when
CLKOUTx_PHASE_CTRL = 00 or 10 for one and 01 for the other.
Use the following convention to interpret the conditions in the
subsequent tables.
- Conditional
- It is safe to time the signals of interest only if the condition in the
header is met. Known skew indicates that the timing between the signals of
interest can be calculated by the timer.
- N/A
- It is always safe to time the signals of interest
regardless of the condition in the header.
- Never Safe
- Signals of interest cannot be safely timed with the given
PD setting regardless of the condition in the header.
Table 1. CLKOUTx Settings that Allow for Safe Timing with
CLKIN
CLKOUTx_PHASE_CTRL |
Known Skew CLKIN→CLKIN_DESKEW |
Info Only: Phase Shift Controlled By |
00 |
Never Safe |
Fixed phase, no deskew |
10 |
Never Safe |
Phase shift interface
1
|
01 |
Conditional |
PD1 |
- Timing based on the
initial phase, same as CLKOUTx_PHASE_CTRL=00.
|
Table 2. CLKOUTx Settings that Allow for Safe Timing with CLKOUTy
(CLKOUTy_PHASE_CTRL=00 or 10)
CLKOUTx_PHASE_CTRL |
Known Skew CLKIN→CLKIN_DESKEW |
Info Only: Phase Shift Controlled By |
00 |
N/A |
Fixed phase, no deskew |
10 |
N/A |
Phase shift interface
1
|
01 |
Never Safe |
PD1 |
- Timing based on the
initial phase, same as CLKOUTx_PHASE_CTRL=00.
|
Table 3. CLKOUTx Settings that Allow for Safe Timing with CLKOUTy
(CLKOUTy_PHASE_CTRL=01)
CLKOUTx_PHASE_CTRL |
Known Skew CLKIN→CLKIN_DESKEW |
Info Only: Phase Shift Controlled By |
00 |
Never Safe |
Fixed phase, no deskew |
10 |
Never Safe |
Phase shift interface
1
|
01 |
N/A |
PD1
2
|
- Timing based on
the initial phase, same as CLKOUTx_PHASE_CTRL=00.
- Both CLKOUTx and CLKOUTy
must have the same frequency which is equivalent to having
the same CLKOUTx_DIVIDE setting. For more information, see
Functioning of Deskew.
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