Lattice Semiconductor ispClock5400D User Manual page 12

Lattice Semiconductor
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.
ispClock5400D Evaluation Board
12
User's Guide