DAC39RF10 datasheet(178/232 Pages) TI2

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Table 8-76. NCO_SS Register Field Descriptions (continued)

Bit

Field

Type

Reset

Description

NCO_SS

R/W

When this bit is set, all NCOs will continuously self-synchronize

every 256 DAC clock cycles.

In a radiation environment, the user can set NCO_SS to continuously

transfer the upset-immune AMP, FREQ and PHASE register values

to the internal (non-immune) registers inside the NCOs. This is

helpful for generating tones under radiation without the need for an

external, periodic synchronization source (such as SYSREF).

NCO_SS can be changed while the NCOs are operating (DP_EN=1).

To write a new FREQ, AMP, or PHASE value, clear NCO_SS first,

and then set it again after the new values are written. All values go

into effect simultaneously on all NCOs.

The user should make sure that NCO_AR=0 whenever NCO_SS=1

(otherwise the NCO accumulators and/or reference counters keep

getting reset).

If the user also sets NCO_SC=1 and NCO_CONT=0, then all four

NCOs maintain coherency with each other under radiation, but there

may be no coherence with an external component. Each NCO

accumulator is continuously seeded from the reference counter in

DUC/DDS channel 0. This feature can be used to generate coherent

harmonic tones to cancel out harmonic distortion in the DAC.

AMP[3:0] Register (Offset = 0318h) [reset = 0000h]

AMP[3:0] is described in Table 8-77. AMP[0] starts at address 0x0318, AMP[1] at address 0x031A, AMP[2] at

address 0x031C and AMP[3] at address 0x031E.

Return to the Register Summary Table.

Table 8-77. AMP[3:0] Register Field Descriptions

Bit

Field

Type

Reset

Description

15-0

AMP[3:0]

R/W

0000h

Specifies the DDS amplitude for DDS channel n. 16-bit signed value.

This register only applies to DDS Operation.

Note: Changes to this register do not take effect until the next sync

event specified by NCO_SYNC_SRC.

Note: This register should only be changed when DP_EN=0 or

updates to the NCOs are scheduled to occur away from the change.

(See NCO_SYNC.)FREQ[0] Register (Offset = 0320h) [reset =

0000000000000000h]

FREQ[0] is described in Table 8-78.

Return to the Register Summary Table.

FREQ for NCO0 Accumulator.

DAC39RF10-SP, DAC39RF10-SEP

DAC39RFS10-SP, DAC39RFS10-SEP

SBAS932A – MARCH 2024 – REVISED FEBRUARY 2026

www.ti.com

178

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