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S-MOS Systems, Inc. 2460 North First Street San Jose, CA 95131 Tel: (408) 922-0200 Fax: (408) 922-0238
268-0.4
81
5.2 – 5.2.2
5.0 Display Control Functions
5.2 Screen Configuration
5.2.1 Screen Configuration
The basic screen configuration of the SED1330F/
1335F/1336F is as a single text screen or as overlap-
ping text and graphics screens. The graphics screen
uses eight times as much display memory as the text
screen.
A/P
Character
memory area
Graphics
memory area
(XM,YM)
(XM,0)
(0,0)
(0,YM)
(XW,YM)
0800H
0000H
Display
memory
window
07FFH
47FFH
C/R
Y
X
Figure 48. Virtual and physical screen relationship
5.2.2 Display Address Scanning
The SED1330F/1335F/1336F scans the display memory
in the same way as a raster scan CRT screen. Each row
is scanned from left to right until the address range
equals C/R. Rows are scanned from top to bottom.
In graphics mode, at the start of each line, the address
counter is set to the address at the start of the previous
line plus the address pitch, AP.
In text mode, the address counter is set to the same
start address, and the same character data is read, for
each row in the character bitmap. However, a new row
of the character generator output is used each time.
Once all the rows in the character bitmap have been
displayed, the address counter is set to the start
address plus AP and the next line of text is displayed.
Figure 40 shows the relationship between the virtual
screens and the physical screen.