XRM(2)-DAC-D4/1G User Guide
V2.2 - Mar 8, 2018
D7 to D0:
D1
XRM board revision (high for rev2 and rev1 boards polarity
correction - redundant)
D0
Phase value mux
The fine control bits for the I and Q channels allow extension of the mark duration in increments of the DACCLK
period. Normally durations can only be stepped in multiples of the FABRCLK period. Setting a value other than
zero modifies the data produced for the last space duration to output the mark level earlier than the 4-clock
boundary. Setting a value greater than 4 effectively reduces the duration of the mark. The use of eight states
allows the waveforms to maintain synchronism at the rising edge of the mark state even if differing mark/space
ratios are programmed.
Note that pulse periods are still constrained to be multiples of FABRCLK cycles
Fine Adjust:
Phase1:
Phase2:
0
4 spaces
0 mark
1
3 spaces
1 marks
2
2 spaces
2 marks
3
1 spaces
3 marks
4
0 spaces
4 marks
5
1 mark
3 spaces
6
2 marks
2 spaces
7
3 marks
1 space
D1 (XRM board revision)-setting this bit high routes DAC data with polarities for rev2 boards; setting this bit low
( the default) routes DAC data with polarities for rev3 boards. This should always be 0 unless a rev2 board is
used.
D0 (Phase value mux) -the default value (0) selects the mid-point/width values of the valid phase window for
readback. A value of selects the start-point/end-point values of the valid phase window for readback.
Sync bit (for synth) -defaults to high since default function is active-low reset of the synth.
Page 85
Register Description
xrm-dac-d4-1g-manual_v2_2.pdf