Datasheet

Classic PCI Configuration Space
65
March 5 2007 − June 2011 SCPS154C
4.54 Link Status Register
The link status register indicates the current state of the PCI Express link. See Table 4−30 for a complete
description of the register contents.
PCI register offset: A2h
Register type: Read-only
Default value: X011h
BIT NUMBER 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RESET STATE 0 0 0 x 0 0 0 0 0 0 0 1 0 0 0 1
Table 4−30. Link Status Register Description
BIT FIELD NAME ACCESS DESCRIPTION
15:13 RSVD R Reserved. Returns 000b when read.
12 SCC R
Slot clock configuration. This bit indicates that the bridge uses the same physical reference clock
that the platform provides on the connector. If the bridge uses an independent clock irrespective of
the presence of a reference on the connector, then this bit must be cleared.
0 = Independent 125-MHz reference clock is used
1 = Common 100-MHz reference clock is used
11 LT R Link training. This bit has no function and is read-only 0b.
10 TE R Retrain link. This bit has no function and is read-only 0b.
9:4 NLW R Negotiated link width. This field is read-only 00 0001b indicating the lane width is 1x.
3:0 LS R Link speed. This field is read-only 1h indicating the link speed is 2.5 Gb/s.
4.55 Serial-Bus Data Register
The serial-bus data register reads and writes data on the serial-bus interface. Write data is loaded into this
register prior to writing the serial-bus slave address register (offset B2h, see Section 4.57) that initiates the
bus cycle. When reading data from the serial bus, this register contains the data read after bit 5 (REQBUSY)
of the serial-bus control and status register (offset B3h, see Section 4.58) is cleared. This register is reset by
a PCI Express reset (PERST
), a GRST, or the internally-generated power-on reset.
PCI register offset: B0h
Register type: Read/Write
Default value: 00h
BIT NUMBER 7 6 5 4 3 2 1 0
RESET STATE 0 0 0 0 0 0 0 0
4.56 Serial-Bus Word Address Register
The value written to the serial-bus word address register represents the word address of the byte being read
from or written to the serial-bus device. The word address is loaded into this register prior to writing the
serial-bus slave address register (offset B2h, see Section 4.57) that initiates the bus cycle. This register is
reset by a PCI Express reset (PERST
), a GRST, or the internally-generated power-on reset.
PCI register offset: B1h
Register type: Read/Write
Default value: 00h
BIT NUMBER 7 6 5 4 3 2 1 0
RESET STATE 0 0 0 0 0 0 0 0
Not Recommended for New Designs