AD5930

Data Sheet

Rev. D | Page 18 of 28

Table 7. Description of Bits in the Control Register

Bit

Name

Function

D15

to

D12

ADDR

Register address bits.

D11

B24

When B24 = 1, a complete word is loaded into a frequency register in two consecutive writes. The first write

contains the 12 LSBs of the frequency word and the next write contains the 12 MSBs. Refer to Table 5 for the

appropriate addresses. The write to the destination register occurs after both words have been loaded, so the

register never holds an intermediate value.

other containing the 12 LSBs. This means that the 12 MSBs of the frequency word can be altered independent of

the 12 LSBs and vice versa. This is useful if the complete 24-bit update is not required. To alter the 12 MSBs or the

12 LSBs, a single write is made to the appropriate register address. Refer to Table 5 for the appropriate addresses.

D10

DAC ENABLE

When DAC ENABLE = 1, the DAC is enabled.

When DAC ENABLE = 0, the DAC is powered down. This saves power and is beneficial when only using the MSB of

the DAC input data (available at the MSBOUT pin).

D9

SINE/TRI

The function of this bit is to control what is available at the IOUT/IOUTB pins.

When SINE/TRI = 1, the SIN ROM is used to convert the phase information into amplitude information resulting in a

sinusoidal signal at the output.

When SINE/TRI = 0, the SIN ROM is bypassed, resulting in a triangular (up-down) output from the DAC.

D8

MSBOUTEN

When MSBOUTEN = 1, the MSBOUT pin is enabled.

When MSBOUTEN = 0, the MSBOUT is disabled (tri-state).

D7

CW/BURST

When CW/BURST = 1, the AD5930 outputs each frequency continuously for the length of time or number of output

When CW/BURST = 0, the AD5930 bursts each frequency for the length of time/number of cycles specified in the

outputs a DC value of midscale. In external increment mode, it is defined by the pulse widths on the CTRL pin.

D6

INT/EXT

BURST

This bit is active when D7 = 0 and is also used in conjunction with D5. When the user is incrementing the frequency

externally (D5 = 1), D6 dictates whether the user is controlling the burst internally or externally.

When INT/EXT BURST = 1, the output burst is controlled externally through the CTRL pin. This is useful if the user is

using an external source to both trigger the frequency increments and determine the burst interval.

When INT/EXT BURST = 0, the output burst is controlled internally. The burst is pre-programmed by the user into

When D5 = 0, this bit is ignored.

D5

INT/EXT

INCR

When INT/EXT INCR = 1, the frequency increments are triggered externally through the CTRL pin.

When INT/EXT INCR = 0, the frequency increments are triggered automatically.

D4

MODE

The function of this bit is to control what type of frequency sweep is carried out.

When MODE = 1, the frequency profile is a saw sweep.

When MODE = 0, the frequency profile is a triangular (up-down) sweep.

D3

SYNCSEL

This bit is active when D2 = 1. It is user-selectable to pulse at the end of sweep (EOS) or at each frequency

increment.

When SYNCSEL = 1, the SYNCOP pin outputs a high level at the end of the sweep and returns to zero at the start of

the subsequent sweep.

D2

SYNCOUTEN

When SYNCOUTEN= 1, the SYNC output is available at the SYNCOP pin.

When SYNCOUTEN= 0, the SYNCOP pin is disabled (tri-state).

D1

Reserved

This bit must always be set to 1.

D0

Reserved

This bit must always be set to 1.