Datasheet

AD9880
Rev. 0 | Page 25 of 64
Hex
Address
Read/Write
or Read Only Bits
Default
Value Register Name
Description
0x17 Read [3:0] ****0000
Hsyncs Per Vsync
MSB
MSB of Hsyncs per Vsync.
0x18 Read [7:0] 00000000 Hsyncs Per Vsync Hsyncs per Vsync count.
0x19 Read/Write [7:0] 00001000 Clamp Placement
Number of pixel clocks after trailing edge of Hsync to begin
clamp.
0x1A Read/Write [7:0] 00010100 Clamp Duration Number of pixel clocks to clamp.
0x1B Read/Write [7] 0******* Red Clamp Select 0 = clamp to ground.
1 = clamp to midscale.
[6] *0****** Green Clamp Select 0 = clamp to ground.
1 = clamp to midscale.
[5] **0***** Blue Clamp Select 0 = clamp to ground.
1 = clamp to midscale.
[4] ***0****
Clamp During Coast
Enable
0 = don’t clamp during Coast.
1 = clamp during Coast.
[3] ****0*** Clamp Disable 0 = internal clamp enabled.
1 = internal clamp disabled.
[1] ******1*
Programmable
Bandwidth
0 = low bandwidth.
1 = full bandwidth.
[0] *******0 Hold Auto Offset 0 = normal auto offset operation.
1 = hold current offset value.
0x1C Read/Write [7] 0******* Auto Offset Enable 0 = manual offset.
1 = auto offset using offset as target code.
[6:5] *10***** Auto Offset 00 = every clamp.
Update Mode 01 = every 16 clamps.
10 = every 64 clamps.
11 = Every Vsync.
[4:3] ***01*** Difference Shift 00 = 100% of difference used to calculate new offset.
Amount 01 = 50%.
10 = 25%.
11 = 12.5%.
[2] *****1** Auto Jump Enable 0 = normal operation.
1 = if code > 15 codes off then offset is jumped to the predicted
offset necessary to fix the > 15 code mismatch.
[1] ******1* Post Filter Enable 0 = disable post filer.
1 = enable post filter.
Post filter reduces update rate by 1/6 and requires that all six
updates recommend a change before changing the offset. This
prevents unwanted offset changes.
[0] *******0 Toggle Filter Enable
The toggle filter looks for the offset to toggle back and forth and
holds it if triggered. This is to prevent toggling in case of missing
codes in the PGA.
0x1D Read/Write [7:0] 00001000 Slew Limit Limits the amount the offset can change by in a single update.
0x1E Read/Write [7:0] 32
Sync Filter Lock
Threshold
Number of clean Hsyncs required for sync filter to lock.
0x1F Read/Write [7:0] 50
Sync Filter Unlock
Threshold
Number of missing Hsyncs required to unlock the sync filter. Counter
counts up if Hsync pulse is missing and down for a good Hsync.
0x20 Read/Write [7:0] 50
Sync Filter Window
Width
Width of the window in which Hsync pulses are allowed.
0x21 Read/Write [7] 1******* SP Sync Filter Enable
Enables Coast, Vsync duration, and Vsync filter to use the
regenerated Hsync rather than the raw Hsync.