
AXI Bridge for PCI Express v2.4
34
PG055 June 4, 2014
Chapter 2:
Product Specification
Root Port Status/Control Register (Offset 0x148)
The Root Port Status/Control register provides access to Root Port specific status and
control. This register is only implemented for Root Port cores. For non-Root Port cores,
reads return 0 and writes are ignored (described in
21:20 Directed Link
Change
RW
0
Directs LTSSM to initiate a link width and/or speed change.
• 00b: No change
• 01b: Force link width
• 10b: Force link speed
• 11b: Force link width and speed
31:22 Reserved
RO
0
Reserved
Table 2-15:
PHY Status/Control Register
(Cont’d)
Bits
Name
Core
Access
Reset
Value
Description
Table 2-16:
Root Port Status/Control Register
Bits
Name
Core
Access
Reset
Value
Description
0
Bridge Enable
RW
0
When set, allows the reads and writes to the AXIBARs to be
presented on the PCIe bus. Root Port software needs to write 1
to this bit when enumeration is done. AXI Enhanced PCIe Bridge
clears this location when link up to link down transition occurs.
Default is set to 0.
15:1
Reserved
RO
0
Reserved.
16
Error FIFO Not
Empty
RO
0
Indicates that the Root Port Error FIFO has data to read.
17
Error FIFO
Overflow
RW1C
0
Indicates that the Root Port Error FIFO overflowed and an error
message was dropped. Writing a 1 clears the overflow status.
18
Interrupt FIFO Not
Empty
RO
0
Indicates that the Root Port Interrupt FIFO has data to read.
19
Interrupt FIFO
Overflow
RW1C
0
Indicates that the Root Port Interrupt FIFO overflowed and an
interrupt message was dropped. Writing a 1 clears the overflow
status
27:20 Completion
Timeout
RW
0
Sets the timeout counter size for Completion Timeouts.
31:28 Reserved
RO
0
Reserved.