54 284 242 223 211 199 188 162 147 100 79 40 39 18 37 16 55
PC Interfacing, Communications and Windows Programming
Cache address lines
Cache control lines
11.6 PCI interface
The TXC supports up to four PCI busmasters and provides the interface between PCI and main memory. It can operate the PCI interface at 25 MHz, 30 MHz or 33 MHz. When used as a PCI master the PIIX3 runs cycles on behalf of DMA, ISA masters or a bus master IDE.
11.7 82091AA (AIP)
The AIP device integrates the serial ports, parallel ports and floppy disk interfaces. Figure 11.3 shows its connections and Figure 11.4 shows the interconnection between the AIP and the PIIX3 device. The OSC frequency is set to 14.21818 MHz. It can be seen that the range of interrupts for the serial, parallel and floppy disk drive is IRQ3, IRQ4, IRQ5, IRQ6 and IRQ7. Normally the settings are:
IRQ3. Secondary serial port (COM2/COM4).
IRQ4. Primary serial port (COM1/COM3).
IRQ6. Floppy disk controller.
IRQ7. Parallel port (LPT1).
Figure 11.4 shows the main connections between the TXC, PIIX3 and the AIP. It can be seen that the AIP uses many of the ISA connections (such as 0WS , IOCHRDY, and so on). The interface between the TXC and the PIIX3 defines the PCI bus and the interface be- tween the PIIX3 and AIP defines some of the ISA signals. It can be seen that the AIP can support up to 8 DMA transfers (DRQ0–DRQ7).