ADN2806

Rev. 0 | Page 14 of 20

Squelch data outputs or clock outputs mode is selected when

CTRLC[1] is 1. In this mode, when the SQUELCH input is

driven to a high state, the DATAOUTN and DATAOUTP pins

are squelched. When the SQUELCH input is driven to a low

state, the CLKOUTN and CLKOUTP pins are squelched. This is

especially useful in repeater applications, where the recovered

clock may not be needed.

driving multiple peripherals. Two inputs, serial data (SDA) and

serial clock (SCK), carry information to and from any device

connected to the bus. Each slave device is recognized by a

unique address. The ADN2806 has two possible 7-bit slave

addresses for both read and write operations. The MSB of the

7-bit slave address is factory programmed to 1. B5 of the slave

address is set by Pin 19, SADDR5. Slave Address Bits [4:0] are

defaulted to all 0s. The slave address consists of the seven MSBs

of an 8-bit word. The LSB of the word either sets a read or write

operation (see Figure 6). Logic 1 corresponds to a read operation,

while Logic 0 corresponds to a write operation.

To control the device on the bus, the following protocol must be

followed. First, the master initiates a data transfer by establish-

ing a start condition, defined by a high-to-low transition on

SDA while SCK remains high. This indicates that an address/

data stream follows. All peripherals respond to the start condition

and shift the next eight bits (the 7-bit address and the R/W bit).

The bits are transferred from MSB to LSB. The peripheral that

recognizes the transmitted address responds by pulling the data

line low during the ninth clock pulse. This is known as an

acknowledge bit. All other devices withdraw from the bus at

this point and maintain an idle condition. The idle condition is

where the device monitors the SDA and SCK lines, waiting for

the start condition and correct transmitted address. The R/W

bit determines the direction of the data. Logic 0 on the LSB of

the first byte means that the master writes information to the

peripheral. Logic 1 on the LSB of the first byte means that the

master reads information from the peripheral.

The ADN2806 acts as a standard slave device on the bus. The data

on the SDA pin is eight bits long, supporting the 7-bit addresses

plus the R/W bit. The ADN2806 has eight subaddresses to enable

the user-accessible internal registers (see Table 6 through Table

10). It, therefore, interprets the first byte as the device address

and the second byte as the starting subaddress. Auto-increment

mode is supported, allowing data to be read from or written to

the starting subaddress and each subsequent address without

manually addressing the subsequent subaddress. A data transfer

is always terminated by a stop condition. The user can also

access any unique subaddress register on a one-by-one basis

without updating all registers.

Stop and start conditions can be detected at any stage of the

data transfer. If these conditions are asserted out of sequence

with normal read and write operations, they cause an immediate

jump to the idle condition. During a given SCK high period, the

user should issue one start condition, one stop condition, or a

single stop condition followed by a single start condition. If an

invalid subaddress is issued by the user, the ADN2806 does not

issue an acknowledge and returns to the idle condition. If the

user exceeds the highest subaddress while reading back in auto-

increment mode, then the highest subaddress register contents

continue to be output until the master device issues a no acknow-

ledge. This indicates the end of a read. In a no-acknowledge

condition, the SDATA line is not pulled low on the ninth pulse.

See Figure 7 and Figure 8 for sample write and read data transfers

and Figure 9 for a more detailed timing diagram.

System Reset

A frequency acquisition can be initiated by writing a 1 followed

frequency acquisition while keeping the ADN2806 in its

previously programmed operating mode, as set in Registers

CTRL[A], CTRL[B], and CTRL[C].