Z90251 ZILOG [Zilog, Inc.], Z90251 Datasheet - Page 31

• Manufacturer Part Number: Z90251
• Description: eZVision 200 Television Controllers with OSD
• Manufacturer: ZILOG [Zilog, Inc.]

Bit 4, Sync Polarity, provides the polarity of the H
and V
provide flexibility for TV chassis designers.
Figure 8
Bit 3, Character Size, sets the size of the characters that are displayed. Character
sizes 1X, 2X, double width and double height are supported. The default value is
1X.
To change the size of the characters in a row, alter the value of the bit during the
previous horizontal interrupt. The character size of the first row is programmed
during vertical interrupt (V
Bits 2, 1, and 0, Vertical Retrace Blanking, set a time period when the OSD is
disabled while the electron gun returns from the bottom to the top of the screen,
and all VBLANK and RGB output are disabled. The blanking period is determined
by counting horizontal pulses according to the following formula:
THL: one horizontal period
The retrace blanking bits, OSD_CNTL (2,1,0) must be set to deactivate the
electron guns during the retrace period.
Bit/
Field
OSD Blank
VRAM Mode
Sync Polarity
Character Size
Vertical Retrace Blanking
Blanking Period=(4 x (Vertical Retrace Blanking)+2) x THL
SYNC
Positive and Negative Sync Signals
must have the same polarity (see Figure 8). This feature is designed to
SYNC
Bit
Position R/W
7
6, 5
4
3
2, 1, 0
) processing. Character size is a row attribute.
32 KB Television Controller with OSD
R/W
R/W
R/W
R/W
R/W
Value Description
00
01
10
11
0
1
0
1
0
1
SYNC
Positive SYNC
Negative SYNC
Enable OSD - POR default
Disable OSD
Select 10-row buffer mode
Reserved
Select 2-row buffer mode
Reserved
Positive
Negative
1X
2X
Retrace Blanking
and V
SYNC
signals. H
PS001301-0800
SYNC
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