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21555 Non-Transparent PCI-to-PCI Bridge User Manual 3
Contents
Contents
1 Preface ..........................................................................................................................................11
1.1 Cautions and Notes ............................................................................................................12
1.2 Data Units ...........................................................................................................................12
1.3 Numbering ..........................................................................................................................12
1.4 Signal Nomenclature ..........................................................................................................13
1.5 Register Abbreviations........................................................................................................14
2 Introduction....................................................................................................................................15
2.1 Comparing a 21555 to a Transparent PPB.........................................................................15
2.2 Architectural Overview........................................................................................................18
2.2.1 Data Buffers...........................................................................................................18
2.2.2 Registers................................................................................................................18
2.2.3 Control Logic..........................................................................................................18
2.3 Special Applications............................................................................................................20
2.3.1 Primary Bus VGA Support .....................................................................................20
2.3.2 Secondary Bus VGA Support ................................................................................20
2.4 Programming Notes............................................................................................................20
2.4.1 Addressing.............................................................................................................20
2.4.2 Transaction Forwarding .........................................................................................21
2.4.3 ROM Access..........................................................................................................21
3 Signal Descriptions........................................................................................................................23
3.1 Primary PCI Bus Interface Signals .....................................................................................24
3.2 Primary PCI Bus Interface 64-Bit Extension Signals ..........................................................26
3.3 Secondary PCI Bus Interface Signals.................................................................................28
3.4 Secondary PCI Bus Interface 64-Bit Extension Signals .....................................................30
3.5 Miscellaneous Signals ........................................................................................................31
4 Address Decoding .........................................................................................................................33
4.1 CSR Address Decoding......................................................................................................34
4.2 Expansion ROM Address Mapping (Decoding) ..................................................................34
4.3 Memory 0 Transaction Address Decoding..........................................................................34
4.3.1 Using the BAR Setup Registers.............................................................................35
4.3.2 Direct Address Translation ....................................................................................36
4.3.3 Lookup Table Based Address Translation.............................................................37
4.3.4 Lookup Table Entry Format ...................................................................................40
4.3.5 Forwarding of 64-Bit Address Memory Transactions.............................................41
4.4 I/O Transaction Address Decoding.....................................................................................42
4.4.1 Indirect I/O Transaction Generation.......................................................................42
4.4.2 Subtractive Decoding of I/O Transactions .............................................................44
4.5 Configuration Accesses ......................................................................................................44
4.5.1 Type 0 Accesses to 21555 Configuration Space...................................................44
4.5.2 Initiation of Configuration Transactions by 21555..................................................45
4.6 21555 Bar Summary...........................................................................................................47
5 PCI Bus Transactions....................................................................................................................49
5.1 Transactions Overview .......................................................................................................49