Z90251 Datasheet, PDF (30/97 Pages) Zilog, Inc. – eZVision 200 Television Controllers with OSD

Z90255 ROM and Z90251 OTP
32 KB Television Controller with OSD
22
5 On-Screen Display
The On-Screen Display (OSD) module generates and displays a 10 row by 24
columns of 512 characters at 14 x 18-dots resolution. The color of each character
can be specified independently.
The televison OSD controller uses H_SYNC and V_SYNC signals to synchronize its
internal circuitry to the video signal, then outputs RGB and Video Blank (VBLANK)
signals. The VBLANK signal is used to multiplex the OSD signal and video signal
onto the screen. The result is that the On-Screen Display is superimposed over
the TV picture.
The display results from the successful timing of several components:
• OSD Positioning
• Second Color Feature
• Mesh and Halftone Effect
• OSD Fade
• Inter-Row Spacing
• Character Generation
5.1 OSD Position
OSD Positioning is controlled by programming the following registers:
• OSD Control Register (Table 8)
• Vertical Position Register (Table 9)
• Horizontal Position Register (Table 10)
OSD Control Register
Table 8 OSD Control Register 00h:Bank A (OSD_CNTL)
Bit
7
6
5
4
3
2
1
0
R/W
Reset
R/W R/W R/W R/W R/W R/W R/W R/W
0
x
x
x
x
x
x
x
Note: R = Read W = Write X = Indeterminate
PS001301-0800