Z90251 Datasheet, PDF (32/97 Pages) Zilog, Inc. – eZVision 200 Television Controllers with OSD

Z90255 ROM and Z90251 OTP
32 KB Television Controller with OSD
24
Vertical Position Register
The Vertical Position Register (Table 6) sets the vertical placement of the OSD on
the screen. The unit of measure for placement is the number of scan lines from
the top of the TV field.
Table 9 Vertical Position Register 01h:Bank A (VERT_POS)
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
0
0
0
0
0
0
0
Note: R = Read W = Write X = Indeterminate
Bit/
Field
reserved
Bit
Position
7
Character double 6
height
R/W Value Description
R
0 Return 0
W 1 No effect
R/W 0 Normal when bit 3 of OSD_CNTL is 0.
2X when bit 3 of OSD_CNTL is 1.
Vertical Position
5,4,3,2,1,0 R/W
1 Double height when bit 3 of OSD_CNTL
is 0.
Double width when bit 3 of OSD_CNTL
is 1.
Vertical position control
The value required for this register can be computed using the following equation:
VERT_POS = (V_POS - 6) / 4
VERT_POS represents the contents of bits 5,4,3,2,1,0 of the Vertical Position
Register (VERT_POS). The default value is 0. When the value is 0, the OSD is at
the top-most OSD position on the screen, with an offset of 06h scan lines above
the OSD area.
VERT_POS is the number of scan lines from the V_SYNC to the OSD start position.
V_POS must be a positive integer with a minimum value of Ah incrementing by 4.
PS001301-0800