Datasheet

3−6
CRT
VGA
Controller
Audio
Codec
PCI1520
19 4
Zoomed Video
Port
PCM
Audio
Input
PCI Bus
PC Card
Interface
Video
Audio
19
4
PC Card
Motherboard
Speakers
Figure 3−4. Zoomed Video Implementation Using the PCI1520
Not shown in Figure 3−4 is the multiplexing scheme used to route either socket 0 or socket 1 ZV source to the graphics
controller. The PCI1520 provides ZVSTAT, ZVSEL0
, and ZVSEL1 signals on the multifunction terminals to switch
external bus drivers. Figure 3−5 shows an implementation for switching between three ZV streams using external
logic.
ZVSTAT
ZVSEL0
ZVSEL1
PCI1520
2
0 1
Figure 3−5. Zoomed Video Switching Application
Figure 3−5 illustrates an implementation using standard three-state bus drivers with active-low output enables.
ZVSEL0
is an active-low output indicating that the socket 0 ZV mode is enabled, and ZVSEL1 is an active-low output
indicating that socket 1 ZV is enabled. When both sockets have ZV mode enabled, the PCI1520 by defaults indicates
socket 0 enabled through ZVSEL0
; however, bit 5 (PORT_SEL) in the card control register (see Section 4.32) allows
software to select the socket ZV source priority. Table 3−3 illustrates the functionality of the ZV output signals.