Limitations when a 256 kbit Memory is Used
1-screen display
The following control registers have fixed values.
Dynamic image display
The following control registers are taken as the display setting.
[KOUT-B]
[KOUT-A]
[MVS1]
[MVS0]
Description
L
No sub-screen
L
H
L
Screen A is displayed
H
L
H
Screen B is displayed
H
Illegal combination
Control register table
Control register table for 256 kbyte systems.
Bit
MSB
LSB
Address
7
6
5
4
3
2
1
0
Description
01H
SBY
STL
N/P
L
VDFS1
VDFS0
L
H
Active mode
02H
L
MVS0
KOUT-B
KOUT-A
FVP
FHP
Display mode
See item “Dynamic image display” above.
Registers starting at address 03H function the same as when 1 Mbit of memory is used.
Multi-mode systems
The multi-mode function cannot be used with 256 kbit VRAM since V-dancing occurs in dynamic images.
Notes on multi-mode (NTSC-PAL)
External memory
Multi-mode can only be used when 1M of external memory is provided.
Operating mode
Since vertical dancing occurs in moving images in modes other than two-screen frame mode, this can only be used
with static images.
When the main screen is NTSC and the subscreen is PAL, images will be expanded vertically. As a result, images may
go offscreen in the 3 and 4 screen field modes.
Vertical compression ratio
Since the number of scan lines in NTSC and PAL differ, the ratios differ by 1/3 in accordance with the ratio of the
number of scan lines.
LC7442, 7442E
No. 4412-11/22
[MOD1] = L
[MOD0] = H
[FLD-B] = L
[FLD-A] = L
KOUT-B and KOUT-A cannot be high at the same time (only 1 screen can be displayed)
2-screen filed mode