Intel GD82559ER manual PCI Latency Timer, PCI Header Type, PCI Base Address Registers, Datasheet

Models: GD82559ER

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Networking Silicon — GD82559ER

Note: Bit 3 is set to 1b only if the value 00001000b (8H) is written to this register, and bit 4 is set to 1b only if the value of 00010000b (16H) is written to this register. All other bits are read only and will return a value of 0b on read.

This register is expected to be written by the BIOS and the 82559ER driver should not write to it.

7.1.7PCI Latency Timer

The Latency Timer register is a byte wide register. When the 82559ER is acting as a bus master, this register defines the amount of time, in PCI clock cycles, that it may own the bus.

7.1.8PCI Header Type

The Header Type register is a byte read only register. It is hard-coded to equal to 00h for a single function card.

7.1.9PCI Base Address Registers

One of the most important functions for enabling superior configurability and ease of use is the ability to relocate PCI devices in address spaces. The 82559ER contains three types of Base Address Registers (BARs). Two are used for memory mapped resources, and one is used for I/O mapping. Each register is 32 bits wide. The least significant bit in the BAR determines whether it represents a memory or I/O space. The figures below show the layout of a BAR for both memory and I/O mapping. After determining this information, power-up software can map the memory and I/O controllers into available locations and proceed with system boot. To do this mapping in a device independent manner, the base registers for this mapping are placed in the predefined header portion of configuration space. Device drivers can then access this configuration space to determine the mapping of a particular device.

31

4 3 2 1 0

Base Address

 

 

 

0

 

 

 

 

 

Prefetchable

Set to 0b in 82559ER

Type

00- locate anywhere in 32-bit address space

01- locate below 1 Mbyte

10- locate anywhere in 64-bit address space

11- reserved

Memory space indicator

Figure 21. Base Address Register for Memory Mapping

Datasheet

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Intel GD82559ER PCI Latency Timer, PCI Header Type, PCI Base Address Registers, Base Address Register for Memory Mapping