GS9062-CFE3 datasheet(37/46 Pages) GENNUM

37 / 46 page

GS9062 Data Sheet

22209 - 7

February 2007

37 of 46

3.9.1 Output Swing

Nominally, the voltage swing of the serial digital output is 800mVp-p single-ended

into a 75

Ω load. This is set externally by connecting the RSET pin to CD_VDD

through 281

Ω .

The output swing may be decreased by increasing the value of the RSET resistor.

The relationship is approximated by the curve shown in Figure 3-5.

Alternatively, the serial digital output swing can drive 800mVp-p into a 50

Ω load.

Since the output swing is reduced by a factor of approximately one third when the

smaller load is used, the RSET resistor must be 187

Ω to obtain 800mVp-p.

Figure 3-5: Serial Digital Output Swing

3.9.2 Serial Digital Output Mute

The GS9062 will automatically mute the serial digital output when the LOCKED

output signal is LOW. In this case, the SDO and SDO signals are set to a constant

voltage level.

3.10 GSPI Host Interface

The GSPI, or Gennum Serial Peripheral Interface, is a 4-wire interface provided to

allow the host to enable additional features of the device and /or to provide

additional status information through configuration registers in the GS9062.

The GSPI comprises a serial data input signal SDIN, serial data output signal

SDOUT, an active low chip select CS, and a burst clock SCLK. The burst clock

must have a duty cycle between 40% and 60%.

Because these pins are shared with the JTAG interface port, an additional control

signal pin JTAG/HOST is provided. When JTAG/HOST is LOW, the GSPI interface

is enabled.

When operating in GSPI mode, the SCLK, SDIN, and CS signals are provided by

the host interface. The SDOUT pin is a high-impedance output allowing multiple

Ω load

300

400

500

600

700

800

900

1000

250 300 350 400 450 500 550 600 650 700

RSET(

Ω)

200

Ω load

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