
Genesis Microchip
gm5060 / gm5060-H Data Sheet
February 2002 
C5060-DAT-01G
54 
Character Mapped OSD Features: 
 
 
 
 
 
 
 
Vertical and/or horizontal magnification of OSD image 
Maximum OSD size: 50 characters horizontal x 20 vertical with full character palette defined 
Background Windows Programming support to define an area in the OSD 
16 levels of blending - suitable for fade effects 
Support for portrait and landscape OSDs (90
0
 rotated fonts) 
Pre and post filter merge of OSD into main graphics channel 
Host update of OSD image while OSD is enabled
4.15.1.1. Character Map and On-chip Font Table 
The content of the character map specifies the message generated by the OSD. 
The character map for the OSD screen is defined by writing into an on-chip character map 
SRAM (3594 words by 24 bits) by means of the host interface. This on-chip memory is also used 
to store programmable font characters, if the fonts are not stored in external frame buffer 
memory. 
In memory, the character map is organized as an array of words, each defining the attributes 
(which character to display, the foreground and background colors, blinking) of one visible 
character on the screen (starting from upper left of the visible character array). In addition, there 
is a row attribute word that appears at the beginning of each row of the array in memory (so that 
the width of the array in memory is one higher than the width of the visible character array). The 
format of these words is described below. 
Registers CHARMAP_XSZ and CHARMAP_YSZ are used to define the visible area of the OSD 
image. For example, Figure 46 shows a character map for which CHARMAP_XSZ =25 and 
CHARMAP_YSZ =10. 
Figure 46. OSD Character Map 
Note that when using on-chip programmable fonts, the character map and the font table share the 
same on-chip RAM. Thus, the size of the character map can be traded off against the number of 
CHARMAP_YSZ 
CHARMAP_XSZ 
Address0: 
Row Attribute 
for 1
 Row 
Address 1: 
Character Attributes for 
character in upper-left 
Address 25: 
Character Attributes for 
character in upper-right 
Address26: 
Row Attribute 
for 2
 Row