PC Interfacing, Communications and Windows Programming
Interrupts usage showing PS/2 port mouse.
The PIIX3 host controller completely supports the standard Universal Host Control- ler Interface (UHCI) and thus, takes advantage of the standard software drivers written to be compatible with UHCI. Its advantages are:
Automatic mapping of function to driver and configuration.
Supports synchronous and asynchronous transfer types.
Self-identifying peripherals that can be hot-plugged.
Supports up to 127 devices.
Supports error-handling and fault-recovery.
Guaranteed bit rate with low delay times.
11.17 Mouse and keyboard interface
The mouse and keyboard interface use the 8242 device, as illustrated in Figure 11.10 It can be seen that the two interrupts which are available are IRQ1 (the keyboard interrupt) and IRQ12 (PS/2 style mouse). If the mouse connects to the serial port then the IRQ12 line does not cause an interrupt. All clock frequencies are derived from the keyboard clock frequency (see Figure 11.6).
11.18 Example ATX motherboard
Figure 11.11 shows an example ATX motherboard. It supports the Pentium II though a Slot 1 SEC socket and is based on Intel 440LX chipset. It is similar to the HX mother- board (which has a Socket 7 processor connector) but has the following:
DIMM connection for up to 384 MB for memory. Support for synchronous 100 MHz DRAM (SDRAM) for a 64/72-bit data path with autodetection for any combination of 4/16/64 MB DRAM modules.