tda8753a NXP Semiconductors, tda8753a Datasheet - Page 5

• Manufacturer Part Number: tda8753a
• Description: Yuv 8-bit Analog-to-digital Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
Analog-to-digital converter
The TDA8753 implements 3 independent CMOS 8-bit
analog-to-digital converters. The converters use a
multi-step approach with offset compensated
comparators.
Clamping
An internal clamping circuit is provided in each of the
3 analog channels. The analog pins INY, INV and INU are
switched to on-chip clamping levels during an active pulse
on the clamp input CLP.The clamping level in the
Y channel is code level 16. The clamping level in the U/V
channel is code level 128 (output code 0 in the
2's complement description) see Tables 3 and 4.
Sample rate converter
A sample rate converter is integrated in the TDA8753A to
facilitate programming of the horizontal aspect ratio which
can be varied from a factor 1 to 2.
This includes conversion from 16/9 to 14/9 and 4/3. In the
U/V channel a linear interpolation is sufficient because of
the four times oversampling.
Discrete time oscillator (DTO)
A discrete time oscillator is used to calculate for every
sample of the phase delay that is needed for a given
compression factor.
Serial interface (SIO)
All controls are sent to the TDA8753A via a serial
microprocessor interface. Data from this interface will be
made active at the vertical input pulse V50.
1996 Jan 12
YUV 8-bit analog-to-digital interface
handbook, halfpage
for address F2
of data value
first data bit
register
(in this example address received is F2 hex)
last address
bit received
Fig.3 Address reception.
1
1
incoming stream
1
5
The TDA8753A has three addressable control registers
which can be loaded via the signals UPDA and UPCL.
The format of this bus is fixed according to mode 0 of the
8051 family UART at 1 Mbaud (8 bits are transmitted, LSB
first).
Serial interface protocol
P
When powered up the SIO is in an unknown state and all
data in the registers is random. When signals are applied
to UPCL and UPDA in this state, the behaviour is
unpredictable. The only way to exit from this state to a
known state is apply a V50 signal to the TDA8753A.
I
From power-on or any other state, the INIT state is entered
(at the latest) one TDA8753A clock period after the end of
the V50 HIGH state. In this state the F0, F1 and F2
TDA8753A registers are loaded with the values that are in
the corresponding line buffers BF0, BF1 and BF2. The first
time V50 is issued after power-on, this data is unknown.
After a rising UPCL edge has been detected, the address
reception state is entered.
A
Bits are counted at each rising UPCL edge. The next 8 bits
received on UPDA line are considered as address bits.
The address reception is illustrated in Fig.3.
NITIALIZATION STATE
OWER
DDRESS RECEPTION STATE
1
0
-
ON STATE
0
1
received
first bit
MBE426
0
Product specification
TDA8753A