z86131 ZiLOG Semiconductor, z86131 Datasheet - Page 13

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

ZiLOG
Z86129/130/131 FUNCTIONAL DESCRIPTION
As discussed, the Z86129/130/131 are defined differently
for the requirements of Line 21 Data applications. However
the part number, Z86129, is used for the Z86129/130/131
functional descriptions. In this description, there are some
descriptions that are not applicable to the Z86130/131 for
the feature differences listed on page 1.
The Z86129 provides full function NTSC, Line 21 perfor-
mance. Input commands are included to enable the decoder
to process and display any of the eight Caption/Text data
channels (CC1, CC2, CC3, CC4, T1, T2, T3 or T4) con-
tained in Line 21 of either field of the incoming video. XDS
data can also be selected for display. The DECODER
ON/OFF commands control whether or not the Line 21 data
in the selected channel is actually displayed. When
switched to the DECODER OFF (TV) state, incoming data
in the selected channel is still processed, but not displayed.
The Z86129/130/131 can also be configured to operate with
PAL or SECAM video signals. It decodes information en-
coded into its VBI in Line 22. The encoded data must con-
form to the waveform and command structure defined for
NTSC Line 21 operation.
VCO Lock
The design includes a VCO with stable gain characteristics
and good power supply rejection. The internal horizontal
and vertical synchronizing circuits provide a high degree
of noise immunity. There are options for both horizontal and
vertical lock. The VCO can be phase locked either to the
horizontal signal derived from the video input signal (VID-
EO) or to the externally supplied HIN signal, typically hor-
izontal flyback.
HIN lock is used to provide a display having a minimum
of observable jitter. This condition requires an HIN signal
derived from the TV display and of the proper polarity. Such
a signal is readily available in a television receiver. VIDEO
lock mode enables the VCO to lock in phase to the incoming
video signal, thus providing good operation in an applica-
tion where no display related HIN signal is available, such
as in a VCR.
Video Timing
Timing signals are derived from the VCO for use in the line
counting and display circuits. Line counting requires proper
identification of the input signal's vertical pulse. Default op-
eration uses the vertical sync signal derived from the video
input signal as the source for vertical lock. This method re-
sults in locking characteristics having good performance
and good noise immunity.
DS007200-TVX0199
P R E L I M I N A R Y
In the event that OSD operation is required under conditions
when no input video is present, it would be necessary to set
the Z86129 for V
is determined from the vertical pulse signal supplied to the
V
The horizontal position of the caption display is determined
by the internal timing circuits. A default condition has been
established that should result in a well centered display in
a typical application. However, because signal delays
through video processing circuits can vary between de-
signs, the Z86129 provides the user with the ability to
change the default timing. No matter which of the horizontal
lock modes are selected, the display horizontal position on
the screen can be adjusted in quarter character (330 ns) steps
by serial port commands.
Displayable Character Set (Z86129 only)
Normal Mode.
ored dot matrix characters on an opaque background. The
Box is normally black but the Z86129 can be set to a blue
background Box with a serial command. The characters are
described by a 12 by 18 dot pattern within a character cell
which is 16 dots wide by 26 dots high per frame. The loca-
tion of the character luminance within the character cell var-
ies from character to character to allow for the display of
lower case letters with descenders. All characters have at
least a 1-dot border of black around each character. Under-
line is also provided. Figure 7 illustrates the Z86129 stan-
dard character map and font.
The character ROM consists of a 12 by 18 dot matrix pattern
per character. Alternate rows and columns are read out in
each field to produce an interleaved and rounded character.
A display row contains a maximum of 32 characters plus a
leading and trailing black box, each a character cell in width,
making the overall width of a display row 34 x 8 = 272 dots.
Successive display rows are butted together so that the total
display occupies 195 dots high.
The black box 34 character cells wide by 195 dots high re-
sults in a box size of 45.018 µs in width by 195 scan lines
in height. The Box starts in scan line 43 and extends to scan
line 237. Theoretically, the display is horizontally centered
in the video display when the Box starts 13.2 µs after the
leading edge of H.
The default setting of the Z86129 places the center of the
Box at about 13.5 µs to allow for some delay in the normal
video path. However, the Box horizontal position can be ad-
justed by the user in 330 ns increments. The display is ap-
proximately within the safe title area for NTSC receivers.
IN
pin.
Characters are displayed as white or col-
IN
lock. In this mode, the vertical timing
NTSC Line 21 Decoder
Z86129/130/131
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