LSI 53C875A - Manual (Page 27)

PCI Functional Description 2-5
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.