Block Diagram
PCI Peripheral Bus Controller (PBC)
The MCPN750A uses the VIA Technologies VT82C586B Peripheral Bus Controller (PBC) to supply the interface between the PCI local bus and the ISA, EIDE and USB systems I/O bus (as shown in Figure
The PBC controller provides the following functions:
❏ISA (Industry Standard Architecture) bus arbitration for DMA devices (Note: feature not used since there are no ISADMA devices).
❏EIDE Interface
❏USB Interface
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❏Seven independently programmable DMA channels (Note: feature not used since there are no ISA DMA devices).
❏Interrupt controller functionality to support 14 ISA interrupts
❏Edge/level control for ISA interrupts
❏Steerable PCI interrupts (Note: feature not used. Interrupt steering via Raven ASIC).
❏Three interval counters/timers (82C54 functionality)
Accesses to the configuration space for the PBC are performed by way of the CONADD and CONDAT (Configuration Address and Data) registers in the Raven bridge controller ASIC. The registers are located at offsets $CF8 and $CFC, respectively, from the PCI I/O base address.
ISA Interface
The PBC provides an ISA bus compatible interface. The ISA interface provides programmable timing and chip selects for ISA compatible peripherals. The ISA bus is used to interface to the serial port’s NVRAM/RTC chip and various board status registers.
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