HP Vectra XA 5/xxx HP Vectra xA 5/XXX Series 5 /vl 5/xxx series 5 pc Technical - Page 25
PCI Bus Interface, ISA Bus Interface, IDE Controller, USB Controller, DMA Controller, Interrupt
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2 System Board Chip-Set PCI Bus Interface ISA Bus Interface IDE Controller USB Controller DMA Controller Interrupt Controller Counter / Timer PCI/ISA Bridge Chip (82371SB) This chip is encapsulated in a 208 pin plastic quad flat pack (PQFP) package. This part of the chip performs PCI-to-ISA, and ISA-to-PCI bus cycle translation. It supports the Plug-and-Play mechanism. As well as accepting cycles from the PCI bus interface, and translating them for the ISA bus, the ISA bus interface also requests the PCI master bridge to generate PCI cycles on behalf of a DMA or ISA master. The ISA bus interface contains a standard ISA bus controller and data buffering logic. It can directly support six ISA slots without external data or address buffering. The PCI master/slave IDE controller, supporting four devices, two on each of two channels, is described on page 34. The PCI USB controller, supporting two connectors, is described on page 36. The seven channel DMA controller incorporates the functionality of two 82C37 DMA controllers. Channels 0 to 3 are for 8-bit DMA devices, while channels 5 to 7 are for 16-bit devices (see page 82). The channels can be programmed for any of the four transfer modes: the three active modes (single, demand, block), can perform three different types of transfer: read, write and verify. The address generation circuitry can only support a 24-bit address for DMA devices. The sixteen channel interrupt controller incorporates the functionality of two 82C59 interrupt controllers. The two controllers are cascaded, giving 14 external and two internal interrupt sources (see page 82). The chip contains a three-channel 82C54 counter/timer. The counters use a division of the 14.31818 MHz OSC input as the clock source. 25