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Adapter Internal Registers
A-21
Register Definitions
A.3 Adapter Internal Registers
The adapter’s internal registers are indirectly accessible from the PCI bus
through the DIO_ADR and DIO_DATA registers. These are usually referred to
as DIO. ThunderLAN has an internal 32-bit bus that is used for DIO accesses
to the registers and the SRAM. PCI bus byte enables are maintained on this
internal bus, allowing arbitrary byte transfers.
DIO accesses are primarily used to initialize and control the ThunderLAN con-
troller. Normally, only ThunderLAN controller registers are accessible by DIO.
In adapter test mode (PCI configuration option), the SRAM, FIFO control regis-
ters, and some PCI controller registers are also accessible.
The content and meaning of some registers vary with the network protocol in
use. The following subsections describe the functions of each register accord-
ing to the protocol.