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# Command Register Bits

Constants that you use to access specific bits of the command register.

## Topics

### Bits

[`kIOPCICommandIOSpace`](/documentation/PCIDriverKit/kIOPCICommandIOSpace)

The bit that indicates whether the device allows access to I/O space.

[`kIOPCICommandMemorySpace`](/documentation/PCIDriverKit/kIOPCICommandMemorySpace)

The bit that indicates whether the device allows access to memory space.

[`kIOPCICommandBusMaster`](/documentation/PCIDriverKit/kIOPCICommandBusMaster)

The bit that controls the ability to issue or forward memory and I/O requests.

[`kIOPCICommandSpecialCycles`](/documentation/PCIDriverKit/kIOPCICommandSpecialCycles)

The bit that enables the legacy special cycle feature.

[`kIOPCICommandMemWrInvalidate`](/documentation/PCIDriverKit/kIOPCICommandMemWrInvalidate)

The bit that enables legacy memory writing and invalidation.

[`kIOPCICommandPaletteSnoop`](/documentation/PCIDriverKit/kIOPCICommandPaletteSnoop)

The bit that enables the legacy palette snooping feature.

[`kIOPCICommandParityError`](/documentation/PCIDriverKit/kIOPCICommandParityError)

The bit that controls the logging of poisoned transaction-layer packets.

[`kIOPCICommandAddressStepping`](/documentation/PCIDriverKit/kIOPCICommandAddressStepping)

The bit that controls the legacy address stepping and wait cycle feature.

[`kIOPCICommandSERR`](/documentation/PCIDriverKit/kIOPCICommandSERR)

The bit that enables the upstream reporting of fatal and non-fatal errors.

[`kIOPCICommandFastBack2Back`](/documentation/PCIDriverKit/kIOPCICommandFastBack2Back)

The bit that enables legacy fast back-to-back transactions.

[`kIOPCICommandInterruptDisable`](/documentation/PCIDriverKit/kIOPCICommandInterruptDisable)

The bit that prevents the generation of INTx emulation interrupts.

[`kIOPCICommandBusLead`](/documentation/PCIDriverKit/kIOPCICommandBusLead)


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