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Raven PCI Bridge ASIC

IDSEL connected to the address bit being asserted will be selected for a configuration cycle. The Raven decodes the Device Number to determine which of the upper address lines to assert. The decoding of the five-bit Device Number is show below:.

Device Number

Address Bit

 

 

00000

AD31

 

 

00001 - 01010

All Zeros

 

 

01011

AD11

 

 

01100

AD12

 

 

(etc.)

(etc.)

 

 

11101

AD29

 

 

11110

AD30

 

 

11111

All Zeros

 

 

The Bus Number determines which bus is the target for the configuration read cycle. The Raven will always host PCI bus #0. Accesses that are to be performed on the PCI bus connected to the Raven must have zero programmed into the Bus Number. If the configuration access is targeted for another PCI bus, then that bus number should be programmed into the Bus Number field. The Raven will detect a nonzero field and convert the transaction to a Type 1 Configuration cycle.

Generating PCI Special Cycles

The Raven supports the method stated in PCI Local Bus Specification 2.0 to generate special cycles using Configuration Mechanism #1. To prime the Raven for a special cycle, the host processor must write a 32-bit value to the CONFIG_ADDRESS register. The contents of the write are defined later in this chapter under the CONFIG_ADDRESS register definition. After the write to CONFIG_ADDRESS has been accomplished, the next write to the CONFIG_DATA register causes the Raven to generate a special cycle on the PCI bus. The write data is driven onto AD[31:0] during the special cycle’s data phase.

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Motorola MVME2300 Series manual Generating PCI Special Cycles, Device Number Address Bit