LSI 53C875A 2.3 I/O Read Command, 2.4 I/O Write Command, Reserved Command, Memory Read Command

2.1.2.3 I/O Read Command

The I/O Read command reads data from an agent mapped in I/O address space. All 32 address bits are decoded.

2.1.2.4 I/O Write Command

The I/O Write command writes data to an agent mapped in I/O address space. All 32 address bits are decoded.

2.1.2.5 Reserved Command

The LSI53C875A does not respond to this command as a slave and it never generates this command as a master.

2.1.2.6 Memory Read Command

The Memory Read command reads data from an agent mapped in the Memory Address Space. The target is free to do an anticipatory read for this command only if it can guarantee that such a read has no side effects.

2.1.2.7 Memory Write Command

The Memory Write command writes data to an agent mapped in the Memory Address Space. When the target returns “ready,” it assumes responsibility for the coherency (which includes ordering) of the subject data.

2.1.2.8 Configuration Read Command

The Configuration Read command reads the configuration space of each agent. An agent is selected during a configuration access when its IDSEL signal is asserted and AD[1:0] are 0b00.

2.1.2.9 Configuration Write Command

The Configuration Write command transfers data to the configuration space of each agent. An agent is selected when its IDSEL signal is asserted and AD[1:0] are 0b00.

PCI Functional Description 2-5