
ADV7152
–27–
REV. B
APPE NDIX 4
MULT IPLE PALE T T E APPLICAT IONS
Palette Priority Select Inputs
T he palette priority selection inputs allow up to four separate
palette devices to be used in a single system to drive a single
monitor. T he IOR, IOG and IOB analog video output signals of
each device are connected together, as shown. Signal inputs
(PS0, PS1) determine on a pixel by pixel basis which palette
device drives the monitor. T his allows for implementation of
multiple windows applications with each device acting as an
independent palette. During initialization, each device is as-
signed two match bits, MR16 (PS0) and MR17 (PS1) in Mode
Register MR1. PS0 and PS1 inputs will select one of the prepro-
grammed devices at any instant when PS0, PS1 matches MR16,
MR17, respectively. When PS0 and PS1 do not match these
bits, the DACs of the particular device are shut down, driving
RGB outputs to 0 mA. PS0 and PS1 are multiplexed similar to
the pixel data, thus allowing for subpixel resolution. T he dia-
grams show an example of one ADV7152 operating in conjunc-
tion with three ADV7151’s (Pseudo-Color RAM-DACs). Each
displayed window on the monitor is driven by one of the four
devices. Each device’s analog output signals are connected to-
gether as shown.
Note: Only one palette device is selected at any particular
instant. T he analog output levels of the unselected devices will
be 0 mA.
Other applications for the palette priority function using a mini-
mum of two devices (two ADV7152s or one ADV7152 and one
ADV7151) include:
Cursor Overlay on 24-Bit Graphics
Active Live Video Overlay (from Frame Grabber)
T ext/Character Generation and Overlay
Z
S
= 75
(SOURCE
TERMINATION)
DACs
Z
O
=75
Z
L
= 75
(MONITOR)
(CABLE)
DACs
IOR, IOG, IOB
(DEVICE: 2)
(DEVICE: 1)
IOR, IOG, IOB
Multiple Devices Termination for a Single Monitor
ADV7152
ADV7151 (1)
256 x 30
RAM
256 x 30
PALETTE
PALETTE SELECT BITS
RGB
ANALOG
VIDEO
RGB
ANALOG
VIDEO
VIDEO TO MONITOR
PS0, PS1
256 x 30
PALETTE
RGB
ANALOG
VIDEO
RGB
ANALOG
VIDEO
ADV7151 (2)
ADV7151 (3)
R0–R7
G0–G7
B0–B7
WINDOW 1
(Pseudo-Color)
PS0 = 0: PS1 = 1
WINDOW 3
(Pseudo-Color)
PS0 = 1: PS1 = 1
MONITOR
WINDOW 2
(Pseudo-Color)
PS0 = 1: PS1 = 0
TRUE-COLOR BACKGROUND
PS0 = 0: PS1 = 0
MR16 MR17
0 0
PALETTE SELECT BITS
MR16 MR17
0 1
PALETTE SELECT BITS
MR16 MR17
1 0
PALETTE SELECT BITS
MR16 MR17
1 1
256 x 30
PALETTE
P0–P7
Multiple Devices Driving a Multiwindow Application