EEPROM

Xin

Xout

V

DD

GND

V

DDOUT

X-tal

Y2=27MHz

Y1=27MHz

Y3=27MHz

LV

CMOS

Pdiv1=1

Y4=27MHz

Y5=27MHz

Y6=27MHz

Y7=27MHz

Y8=27MHz

Y9=27MHz

LV

CMOS

Pdiv9=1

Pdiv8=1

LV

CMOS

LV

CMOS

Pdiv7=1

Pdiv6=1

LV

CMOS

LV

CMOS

Pdiv5=1

Pdiv4=1

LV

CMOS

LV

CMOS

Pdiv3=1

Pdiv2=1

LV

CMOS

Programming

and

SDA/SCL

Register

InputClock

PLL Bypass

PLL 1

powerdown

PLL Bypass

PLL 2

powerdown

PLL Bypass

PLL 3

powerdown

PLL Bypass

PLL 4

powerdown

S0

SDA

SCL

27MHz

Crystal

ProgrammingBus

“1” =outputsenabled

“0” =outputs3-State

CDCE949

CDCEL949

SCAS844D – AUGUST 2007 – REVISED MARCH 2010

www.ti.com

Y1 SELECTION

Y1

FUNCTION

0

State 0

1

State 1

(1)

State0 and State1 are user-definable in Generic Configuration

Register and can be power down, 3-state, low or active.

The S1/SDA and S2/SCL pins of the CDCE949/CDCEL949 are dual-function pins. In the default configuration

they are defined as SDA/SCL for the serial interface. They can be programmed as control pins (S1/S2) by setting

the appropriate bits in the EEPROM. Note that changes to the Control register (Bit [6] of Byte 02) have no effect

until they are written into the EEPROM.

forced to GND, the two control-pins, S1 and S2, temporarily act as serial programming pins (SDA/SCL).

S0 is not a multi-use pin, it is a control pin only.

DEFAULT DEVICE SETTING

The internal EEPROM of CDCE949/CDCEL949 is preconfigured as shown in Figure 6. (The input frequency is

passed through to the output as a default.) This allows the device to operate in default mode without the extra

production step of programming it. The default setting appears after power is supplied or after a power-down/up

sequence until it is reprogrammed by the user to a different application configuration. A new register setting is

programmed via the serial SDA/SCL Interface.

Figure 6. Default Configuration

Table 4 shows the default setting for the Control Terminal Register (external control pins). In normal operation, all

8 register settings are available, but in the default configuration only the first two settings (0 and 1) can be

selected with S0, as S1 and S2 are configured as programming pins in default mode.

10

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Product Folder Link(s): CDCE949 CDCEL949