ADF4111 AD [Analog Devices], ADF4111 Datasheet - Page 23

• Manufacturer Part Number: ADF4111
• Description: RF PLL Frequency Synthesizers
• Manufacturer: AD [Analog Devices]

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INTERFACING
The ADF4110 family has a simple SPI-compatible serial inter-
face for writing to the device. SCLK, SDATA and LE control
the data transfer. When LE (Latch Enable) goes high, the 24 bits
which have been clocked into the input register on each rising
edge of SCLK will get transferred to the appropriate latch. See
Figure 1 for the Timing Diagram and Table I for the Latch
Truth Table.
The maximum allowable serial clock rate is 20 MHz. This means
that the maximum update rate possible for the device is 833 kHz or
one update every 1.2 microseconds. This is certainly more than
adequate for systems that will have typical lock times in hundreds
of microseconds.
ADuC812 Interface
Figure 34 shows the interface between the ADF4110 family and
the ADuC812 microconverter. Since the ADuC812 is based on
an 8051 core, this interface can be used with any 8051-based
microcontroller. The microconverter is set up for SPI Master
Mode with CPHA = 0. To initiate the operation, the I/O port
driving LE is brought low. Each latch of the ADF4110 family
needs a 24-bit word. This is accomplished by writing three 8-bit
bytes from the microconverter to the device. When the third
byte has been written the LE input should be brought high to
complete the transfer.
On first applying power to the ADF4110 family, it needs three
writes (one each to the R counter latch, the N counter latch and
the initialization latch) for the output to become active.
I/O port lines on the ADuC812 are also used to control power-
down (CE input) and to detect lock (MUXOUT configured as
lock detect and polled by the port input).
When operating in the mode described, the maximum SCLOCK
rate of the ADuC812 is 4 MHz. This means that the maximum
rate at which the output frequency can be changed will be
166 kHz.
Figure 34. ADuC812 to ADF4110 Family Interface
ADuC812
I/O PORTS
SCLOCK
MOSI
SCLK
SDATA
LE
CE
MUXOUT
(LOCK DETECT)
ADF4110
ADF4111
ADF4112
ADF4113
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ADF4110/ADF4111/ADF4112/ADF4113
ADSP-2181 Interface
Figure 35 shows the interface between the ADF4110 family and
the ADSP-21xx Digital Signal Processor. The ADF4110 family
needs a 24-bit serial word for each latch write. The easiest way
to accomplish this using the ADSP-21xx family is to use the
Autobuffered Transmit Mode of operation with Alternate
Framing. This provides a means for transmitting an entire
block of serial data before an interrupt is generated.
Set up the word length for 8 bits and use three memory loca-
tions for each 24-bit word. To program each 24-bit latch, store
the three 8-bit bytes, enable the Autobuffered mode and then
write to the transmit register of the DSP. This last operation
initiates the autobuffer transfer.
Figure 35. ADSP-21xx to ADF4110 Family Interface
ADSP-21xx
I/O FLAGS
SCLK
TFS
DT
SCLK
SDATA
LE
CE
MUXOUT
(LOCK DETECT)
ADF4110
ADF4111
ADF4112
ADF4113