z86131 ZiLOG Semiconductor, z86131 Datasheet - Page 20

• Manufacturer Part Number: z86131
• Description: Ntsc Line 21 Decoder
• Manufacturer: ZiLOG Semiconductor

Z86129/130/131
NTSC Line 21 Decoder
Z86129/130/131 FUNCTIONAL DESCRIPTION (Continued)
Note: Valid Line 21 waveform is defined as the presence of a
20
channel selected is presented. The autoblanking cir-
cuit is not activate again until a valid Line 21 wave-
form has been lost for 1.5 seconds. Any data received
during the 1.5-second period resets the counter so that
autoblanking is only activated on continuous loss of
the Line 21 waveform for 1.5 seconds.
7-cycle run-in clock and a start bit on Line 21 of the field
being examined.
P R E L I M I N A R Y
4. The fourth method of clearing the screen is by the ac-
tion of the 16 Second Erase Timer. This function is
only active when a CAPTION or XDS display mode
has been selected. If no data is received for the display
channel selected for a 16 second period, the on-screen
memory is erased. The decoder is still in the selected
channel and with the decoder ON, so that when data
for the selected channels resumes, it is displayed.
DS007200-TVX0199
ZiLOG