AD5930
Data Sheet
Rev. | 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
Two write operations are required to load a complete word into the FSTART register and the Δf register.
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 t
o 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.
When B24 = 0, the 24-bit FSTART /Δf register operates as two 12-bit registers, one containing the 12 MSBs and the
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 t
o 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
waveform cycles specified in the appropriate register, TBURST.
When CW/BURST = 0, the AD5930 bursts each frequency for the length of time/number of cycles specified in the
burst register, TBURST. For the remainder of the time within each increment window (TBURST
tINT), the AD5930
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
the TBURST register (the burst interval can either be clock-based or for a specified number of output cycles).
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.
When SYNCSEL= 0, the SYNCOP outputs a pulse of 4 × TCLOCK only at each frequency increment.
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.
B