12
ispClock5400D Evaluation Board
Lattice Semiconductor
User’s Guide
Figure 12. Scope Plot - Phase Skew Adjustment
The waveform shows the BANK_2 output advanced 1.24 ns.
Modify the Reference Clock Source Input
The evaluation board provides both 100 MHz (REFA) and 156.25 MHz (REFB) reference clock sources using on-
board CMOS oscillators. This section demonstrates active clock selection using the ispClock5406D user-program-
mable control and status USER pins, to adjust the on-chip REFSEL signal. In this case, the user signal input
(USER3) acts as a mux control over REFA and REFB input reference clocks.
To modify the reference clock source input:
1.
From PAC-Designer, double-click the
USER Signal Routing Block
.
The USER Pin Function Allocation dialog appears.
2.
Note the REFSEL function input is set to the USER3 pin input.
This allows an external control over the ispClock5406D reference clock source input path.
3.
Click
Cancel
.
4.
Toggle position 3 of the DIP switch (USER3) on the evaluation board to the
0= (zero)
position to enable the
156.25 MHz input reference clock, REFB_P/N input.
5.
Note the updated scope display.
