Texas Instruments 60X - Manual (Page 56)

4-10 Theory of Operation
A simplified block diagram of the M1523 chip is shown in Figure 4-4 and the associated
pinouts are provided in Figure 4-5.
4.3.2.1 ALI M1523 (PCI-ISA Bridge)
The M1523 is a bridge between PCI and ISA bus, providing full PCI and ISA compatible functions. The
M1523 has Integrated System Peripherals (ISP) on-chip and provides advanced features in the DMA
controller. This chip contains the keyboard controller, real-time clock and IDE master controller. This
chip also supports the Advanced Programmable Interrupt controller (APIC) interface.
One eight-byte bidirectional line buffer is provided for ISA/DMA master memory read/writes. One 32-bit
wide posted-write buffer is provided for PCI memory write cycles to the ISA bus. It also supports a PCI to
ISA IRQ routing table and level-to-edge trigger transfer.
The chip has two extra IRQ lines and one programmable chip select for motherboard Plug-and-Play
functions. The interrupt lines can be routed to any of the available ISA interrupts.
The on-chip IDE controller supports two IDE connectors for up to four IDE devices providing an interface
for IDE hard disks and CD-ROMs. The ATA bus pins are dedicated to improve the performance of IDE
master.
The M1523 supports the Super Green feature for Intel and Intel compatible CPUs. It implements
programmable hardware events, software event and external switches (for suspend/turbo/ring-in). The
M1523 provides CPU clock control (STPCLKJ). The STPCLKJ can be active (low) or inactive (high) in
turn by throttling control.