TDA935x Philips, TDA935x Datasheet - Page 98

• Manufacturer Part Number: TDA935x
• Description: TV Signal Processor-Teletext Decoder with Embedded u-Controller
• Manufacturer: Philips

Philips Semiconductors
43. The vertical blanking pulse in the RGB outputs has a width of 27 or 22 lines (50 or 60 Hz system). The vertical pulse
44. The timing pulses for the vertical ramp generator are obtained from the horizontal oscillator via a divider circuit.
45. Conditions: frequency is 50 Hz; normal mode; VS = 1F.
46. The output range percentages mentioned for E-W control parameters are based on the assumption that 400 A
47. The ICs have a zoom adjustment possibility for the horizontal and vertical deflection. For this reason an extra DAC
48. At a chrominance input voltage of 660 mV (p-p) (colour bar with 75% saturation i.e. burst signal amplitude
49. The ACL function can be activated by via the ACL bit in the subaddress 20H. The ACL circuit reduces the gain of the
50. This parameter indicates the bandwidth of the complete chrominance circuit including the chrominance bandpass
51. The subcarrier output is combined with a 3-level switch output which can be used to switch external circuits like
2001 Jan 18
TV signal processor-Teletext decoder with
embedded -Controller
in the sandcastle pulse has a width of 14 or 9.5 lines (50 or 60 Hz system). This to prevent a phase distortion on top
of the picture due to a timing modulation of the incoming flyback pulse.
During TV reception this divider circuit has 3 modes of operation:
a) Search mode ‘large window’.
b) Standard mode ‘narrow window’.
c) Standard TV-norm (divider ratio 525 (60 Hz) or 625 (50 Hz).
The vertical divider needs some waiting time during channel-switching of the tuner. When a fast reaction of the
divider is required during channel-switching the system can be forced to the search window by means of the NCIN bit
in subaddress 25H.
When RGB signals are inserted the maximum vertical frequency is increased to 72 Hz. This has the consequence
that the circuit can also be synchronised by signals with a higher vertical frequency like VGA.
variation in E-W output current is equivalent to 20% variation in picture width.
has been added in the vertical amplitude control which controls the vertical scan amplitude between 0.75 and 1.38
of the nominal scan. At an amplitude of 1.06 of the nominal scan the output current is limited and the blanking of the
RGB outputs is activated. This is illustrated in Fig. 42.
a) The nominal scan height must be adjusted at a position of 19 HEX of the vertical ‘zoom’ DAC.
300 mV (p-p)) the dynamic range of the ACC is +6 and 20 dB.
chroma amplifier for input signals with a chroma-to-burst ratio which exceeds a value of 3.0.
filter. The bandwidth of the low-pass filter of the demodulator is approximately 1 MHz.
sound traps etc. This output is controlled by the CMB1 and CMB0 bits in control byte 22H. The subcarrier signal is
available when CMB1/0 are set to 0/1. During the demodulation of SECAM signals the subcarrier signal is only
available during the vertical retrace period. The frequency is 4.43 MHz in this condition. When CMB1/0 are set to 00
in versions for 90 picture tubes (no EW output) the output is high ohmic.
This mode is switched on when the circuit is not synchronized or when a non-standard signal (number of lines
per frame outside the range between 311 and 314(50 Hz mode) or between 261 and 264 (60 Hz mode) is
received). In the search mode the divider can be triggered between line 244 and line 361 (approximately
45 to 64.5 Hz).
This mode is switched on when more than 15 succeeding vertical sync pulses are detected in the narrow window.
When the circuit is in the standard mode and a vertical sync pulse is missing the retrace of the vertical ramp
generator is started at the end of the window. Consequently, the disturbance of the picture is very small. The
circuit will switch back to the search window when, for 6 successive vertical periods, no sync pulses are found
within the window.
When the system is switched to the narrow window it is checked whether the incoming vertical sync pulses are
in accordance with the TV-norm. When 15 standard TV-norm pulses are counted the divider system is switched
to the standard divider ratio mode. In this mode the divider is always reset at the standard value even if the vertical
sync pulse is missing.
When 3 vertical sync pulses are missed the system switches back to the narrow window and when also in this
window no sync pulses are found (condition 3 missing pulses) the system switches over to the search window.
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TDA935X/6X/8X PS/N2 series
Tentative Device Specification