LAN9420 Datasheet, PDF (27/171 Pages) SMSC Corporation – Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
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3.2.4.2.2
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BA + 3FCh
BA + 200h
BA + 1FCh
BA (BAR3)
CSR - Big Endian (512 Bytes)
CSR - Little Endian (512 Bytes)
Figure 3.3 CSR Double Endian Mapping
I/O MAPPING OF CSR
The I/O BAR (BAR4) is double mapped over the CSR space with the non-prefetchable area. The CSR
big endian space is disabled, as the Host processors (Intel x86) that use the I/O BAR are little endian.
Note: A comparison of Figure 3.3 with Figure 3.4 indicates only the first 256 bytes of CSR little endian
space is addressable via the I/O BAR.
BA + 0FCh
BA (BAR4)
CSR - Little Endian ( 256 Bytes)
Figure 3.4 I/O Bar Mapping
I/O BAR and non-
prefetchable memory
are double mapped to
the CSR space
3.2.4.3
PCI Target Interface Transaction Errors
If the Host system attempts an unsupported cycle type when accessing the CSR via the PCI Target
Interface, a slave transaction error will result and the PCI Target Interface will generate a Slave Bus
Error Interrupt (SBERR_INT), if enabled. CSR may only be read or written as DWORD quantities and
any other type of access is unsupported and will result in the assertion of SBERR_INT. Non-DWORD
reads will return a DWORD while non-DWORD writes are silently discarded. In order to cleanly recover
from this condition, a software reset or H/W reset must be performed. A software reset is accomplished
by setting the SRST bit of the BUS_MODE register.
3.2.4.4
PCI Discard Timer
When the PCI master performs a read of LAN9420/LAN9420i, the PCI Bridge will fetch the data and
acknowledge the PCI transfer when data is available. If the PCI master malfunctions and does
complete the transaction within 32768 PCI clocks, LAN9420/LAN9420i will flush the data to prevent a
potential bus lock-up.
3.2.5 Interrupt Gating Logic
One set of interrupts exists: PCI Host interrupts (PCI interrupts from LAN9420/LAN9420i to the PCI
Host). PCI Host interrupts result from the assertion of the internal IRQ signal from the Interrupt
Controller. Refer to Section 3.3.1, "Interrupt Controller," on page 28 for sources of this interrupt.
Figure 3.5 illustrates how interrupts are sourced by the Interrupt Controller to the PCIB and are
propagated to the Host. The Interrupt is passed on to the Host only when the Host has enabled it by
setting bit 10 in the PCI Device Command Register. The Host may obtain interrupt status by reading
SMSC LAN9420/LAN9420i
27
DATASHEET
Revision 1.6 (07-18-11)