PCI1520 Datasheet, PDF (42/138 Pages) Texas Instruments – PC CARD CONTROLLERS

CRT
Speakers
Motherboard
PCI Bus
VGA
Controller
Zoomed Video
Port
19
Audio
Codec
PCM
Audio
Input
4
PCI1520
PC Card
19
PC Card
Interface
Video
Audio
4
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.
2
PCI1520
ZVSTAT
ZVSEL0
ZVSEL1
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.
3−6