Philips DV29 Gpio control signals from the Vaddis Single Name, Function, Clocks and Spdif stage

Fig 3. GPIO control signals from the Vaddis V

Single Name	I/P-O/P	Function
PSUFSO-1	Output	Control PSU Clock
		divider
ENABLE_AV	Output	SCART control High
		in normal operation
		and low in standby
16/9	Output	Scart 16/9
		anamorphic control
		line
9190INT*	Input	Interrupt signal
		from SII9190 HDMI
		transmitter
GAIN_SCALING	Output	High for HDCD gain
		scaling
ML_8740_0-2	Output	SPI load signal for
		Audio DACs 0,1 and
		2 (see note 1)
MC	Output	SPI clock signal for
		DAC control
MD	Output	SPI data signal for
		DAC control
FSELE0-1	Output	Frequency select
		generator
MUTE*	Output	Active low audio
		mute signal
DDC_SDA,DDC,SCL	I/O	12C bus for DDC
		channel on HDMI
		interface
PROG_INT*	Output	High for Progscan
		mode, Low for
		interlaced mode.
		Controls Sil9130
		data mux
HDMI_RESET*	Output	Reset signal for
		HDMI transmitter
RESET*	Output	System reset

Clocks and SPDIF stage.

IC300 is a SM8707E clock generator IC. This IC is sensitive to noise on it’s power supply, which causes clock jitter for this reason we have a independent Low dropout – low noise +3v3 power supply for the chip based around the regulator at location REG300.

X300 is a 27Mhz crystal that IC300 uses to generate all the video and audio clocks required by the system the crystal sits on the XTI and XTO pins of the chip, the 27Mhz output at Pin 4 (MO2) is used to drive the Vaddis chip directly bypassing the internal PLL.

The frequency of the audio master is dependent on the on the current audio sample rate (I.e the sample rate required by the format CD=44.1Khz and DVD=48khz etc) and this is set by the system micro via the FSLO and FSEL1 this selects either the 22.5792Mhz or 24.576Mhz clock from frequency from IC300 this may then be divided by 2 by the clock divide chip at location IC306 depending on the status of FSEL1. Therefore 4 clock frequencies may be obtained to support all required audio samples rates.

Nand gate IC303 is used to gate FSEL1 with ENABLE_AV (which is low in standby mode) as such when in standby mode the audio clock is disabled.

Clock Buffer

IC301 us used to buffer the audio master clock. The circuit is arranged so that each device that requires the audio master clock has it’s own driver these are seen as.

oMCLK_DAC0 - Pin 18 o MCLK_DAC1 – Pin 16 o MCLK_DAC2 – Pin 14 o MCLK_VADDIS – Pin 3 o MCLK_HDMI – Pin 9

We also run the Mute Line from the Vaddis V IC301 this can be seen on Pin 12 and drives transistor TR401, the transistor pulls the relays RLY400, RLY500, RLY600 to ground and un-mutes the audio outputs.

IS2 Audio Data

IC302 and IC309 are buffers for the 12S signals these ensure that the signals travelling to the DAC’s are point to point. IC302 deals with the ALRCK and ABCLK and IC309 the ADAT0,1,2 all signal are split into three separate lines for the three stereo DACS.

PSU Clock Divider

IC304 and IC305 form a clock divide by 1, 2 or 4 to ensure the PSU clock is always either 44.1kHz or 48Khz (See fig 1 within the power supply description section).

This circuit will also switch the PSUCLK off when switching between sample rates (the PSU will free run when the PSUCLK is not present).

SPDIF Output

The SPDIF output consists of IC308 implemented as a inline buffer and parallel output buffer. Gate A buffers the signal so that the SPDIF line from the VADDIS sees fewer loads and form a feed to the Optical output transmitter, gates B,C and D drive the SPDIF in parallel so that we can drive a 75ohm load adequately. The resistors at the output of IC308 are arrange so that the output will be 500mV pk- pk when the output is terminated with a 75 ohm load at the same time the output impedance of the circuit is 75ohms as required by the Sony Philips Digital Interface specification, the transformer at location TX301 electrically isolates the SPDIS output.