Datasheet
ADF4159 Data Sheet
Rev. D | Page 32 of 36
INTERRUPT MODES AND FREQUENCY READBACK
Interrupt modes are triggered from the rising edge of TX
DATA
.
To activate this function, set Bits DB[30:27] in Register R0 to
1111, and set Bits DB[25:21] in Register R4 to 00010. To sele ct
and enable the interrupt mode, set Bits DB[27:26] in Register R5
as shown in Table 8. A ramp must be active for readback to work.
Table 8. Interrupt Modes (Register R5)
Bits DB[27:26] Interrupt Mode
00 Interrupt is off
01 Interrupt on TX
DATA
, sweep continues
11
Interrupt on TX
DATA
, sweep stops
Figure 50 shows the theory of frequency readback.
FREQUENCYLOGIC LEVEL
TIME
TIME
TIME OF INTERRUPT
FREQUENCY AT WHICH INTERRUPT TOOK PLACE
INTERRUPT SIGNAL
LOGIC HIGH
LOGIC LOW
1. SWEEP CONTINUES MODE
2. SWEEP STOPS MODE
1 2
10849-040
Figure 50. Interrupt and Frequency Readback
When an interrupt takes place, the data, consisting of the INT
and FRAC values, can be read back via MUXOUT. The data
comprises 37 bits: 12 bits represent the INT value and 25 bits
represent the FRAC value. Figure 51 shows how single bits
are read back.
MSB
LSB
MUXOUT
CLK
LE
12-BIT INTEGER WORD
0000 1110 0111
0x0E7
231
25-BIT FRAC WORD
1 0110 0010 0011 1010 0111 1000
0x1623A78
23,214,712
RF =
f
PFD
× (231 + 23,214,712/2
25
) = 1.7922963GHz
TX
DATA
DATA CLOCKED OUT ON POSITIVE EDGE OF CLK AND READ
ON NEGATIVE EDGE OF CLK READBACK WORD (37 BITS)
0 0001 1100 1111 0110 0010 0011 1010 0111 1000 (0x1CF623A78)
10849-041
Figure 51. Reading Back Single Bits to Determine the Output Frequency
at the Moment of Interrupt
For continuous frequency readback, the following sequence
must be used (see Figure 52).
1. Register 0 write
2. LE high
3. Pulse on TX
DATA
4. Frequency readback
5. Pulse on TX
DATA
6. Register R4 write
7. Frequency readback
8. Pulse on TX
DATA
Figure 52 shows the continuous frequency readback sequence.
CL
K
MUX
OUT
L
E
TX
DATA
DATA
R0 W
RITE R4 WRI
TE R4
WRIT
E
FRE
QUENC
Y
RE
ADBACK
FRE
QUE
NCY
RE
ADBACK
FR
EQUE
NCY
RE
ADBACK
37 C
LK
PU
L
SES
37 CLK
PULSES
37
C
LK
PU
LSES
32 CLK
PULSES
32
CL
K
PULSES
32 CLK
P
U
LSES
10849-042
Figure 52. Continuous Frequency Readback