Pentek 6230 Operating Manual page 151

GC4016 MULTI-STANDARD QUAD DDC CHIP
ADDRESS 18: NCO Sync, Suggested default = 0x22
BIT TYPE
0-2 LSB R/W
3 R/W
4-6 R/W
7 MSB R/W
These syncs use the selections shown in Table 7.
The NCO_SYNC can be changed to "SIB" so that the SIB sync can be used to synchronize the NCO phases of multiple
channels or chips.
The DITHER_SYNC is used to turn on or off the dithering of the NCO phase. Dithering is turned on by setting
DITHER_SYNC to "never". Dithering is turned off by setting DITHER_SYNC to "always" which causes it to remain reset to zero.
During diagnostics the NCO_SYNC and DITHER_SYNC should be set to "TC" (5).
If the user wishes to allow the chip to free run, asynchronous to other chips, then these sync settings can be set to "never".
ADDRESS 19: Zero Pad Mode Control Register, Suggested default = 0x20
BIT TYPE
0-3 LSB R/W
4-6 R/W
7 MSB R/W
ADDRESS 20: Dec and Flush Sync Register, Suggested default = 0x22
BIT TYPE
0-2 LSB R/W
3 R/W
4-6 R/W
7 MSB R/W
The decimation counter sync (DEC_SYNC) may be periodic without interrupting processing so long a the sync period is a
multiple of 8N. A decimation sync should be issued if the decimation control is changed.
Each channel should be flushed (FLUSH_SYNC) when the chip is being initialized or when the decimation control is
changed. The flush lasts for 24N clocks after the sync occurs. The channel flush syncs will normally be left in a "never" mode.
During diagnostics the channels will need to be flushed at the beginning of each sync cycle.
The user may wish to flush a channel when a new frequency is selected in order to purge the datapath of the last signal.
© GRAYCHIP,INC.
This document contains information which may be changed at any time without notice
NAME DESCRIPTION
NCO_SYNC The NCO is initialized to the phase setting by this sync
Unused
DITHER_SYNC The dither circuit is reset by this sync to zero.
Unused
NAME DESCRIPTION
NZEROS The number of zeroes to insert between each sample in the blank mode.
Ranges from 0 to 15. Note that this introduces a gain of 1/(NZEROS+1).
ZPAD_SYNC The sync selection from Table 7 for the zero pad function (See Figure 5).
ZPAD_EN Turn on zero padding for this channel.
NAME DESCRIPTION
DEC_SYNC Synchronizes the decimation control counter. The decimation counter controls
the filtering of each channel.
Unused
FLUSH_SYNC Synchronizes the flush sync for this channel.
Unused
- 38 -
DATA SHEET REV 1.0
August 27, 2001