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GD82559ER — Networkin
g
Silicon
14
Datasheet
4.2 PCI Interface
4.2.1 82559ER Bus O
p
erations
After configuration, the 82559ER is ready for normal operation. As a Fast Ethernet controller, the
role of the 82559ER is to access transmitted data or deposit received data. In both cases the
82559ER, as a bus master device, will initiate memory cycles via the PCI bus to fetch or deposit
the required data.
To perform these actions, the 82559ER is controlled and examined by the CPU via its control and
status structures and registers. Some of these control and status structures reside in the 82559ER
and some reside in system memory. For access to the 82559ER’s Control/Status Registers (CSR),
the 82559ER acts as a slave (in other words, a target device). The 82559ER serves as a slave also
while the CPU accesses its 128 Kbyte Flash buffer or its EEPROM. Section 4.2.1.1 describes the
82559ER slave operation. It is followed by a description of the 82559ER operation as a bus master
(initiator) in Section 4.2.1.2, “82559ER Bus Master Operation” on page 18.
4.2.1.1 82559ER Bus Slave O
p
eration
The 82559ER serves as a target device in one of the following cases:
•
CPU accesses to the 82559ER System Control Block (SCB) Control/Status Registers (CSR)
•
CPU accesses to the EEPROM through its CSR
•
CPU accesses to the 82559ER PORT address via the CSR
•
CPU accesses to the MDI control register in the CSR
•
CPU accesses to the Flash control register in the CSR
•
CPU accesses to the 128 Kbyte Flash
The CSR and the Flash buffer are considered by the 82559ER as two totally separated memory
spaces. The 82559ER provides separate Base Address Registers (BARs) in the configuration space
to distinguish between them. The size of the CSR memory space is 4 Kbyte in the memory space
and 64 bytes in the I/O space. The 82559ER treats accesses to these memory spaces differently.
4.2.1.1.1 Control/Status Re
g
ister
(
CSR
)
Accesses
The 82559ER supports zero wait-state
single-cycle memory or I/O-mapped accesses to its CSR
space. Separate BARs request 4 Kbytes of memory space and 64 bytes of I/O space to accomplish
this. Based on its needs, the software driver will use either memory or I/O mapping to access these
registers. The 4 Kbytes of CSR space the 82559ER requests include the following elements:
•
System Control Block (SCB) registers
•
PORT register
•
Flash control register
•
EEPROM control register
•
MDI control register
•
Flow control registers