Chapter 7: Register Descriptions
7–19
PCI Express Avalon-MM Bridge Control Register Access Content
November 2012
Altera Corporation
Arria V GZ Hard IP for PCI Express
Sending a Write TLP
The Application Layer performs the following sequence of Avalon-MM accesses to
the CRA slave port to send a Memory Write Request:
1. Write the first 32 bits of the TX TLP to
RP_TX_REG0.
2. Write the next 32 bits of the TX TLP to
RP_TX_REG1.
3. Write the
RP_TX_CNTRL.SOP
to 1’b1 to push the first two dwords of the TLP into the
Root Port TX FIFO.
4. Repeat Steps
. The second write to
RP_TX_REG1
is required, even for three
dword TLPs with aligned data.
5. If the packet is complete write
RP_TX_CNTRL
to 2’b10 o indicate the end of the
packet. If the packet is not complete write 2’b00 to
RP_TX_CNTRL.
6. Repeat this sequence to program a complete TLP.
When the programming of the TX TLP is complete, the Avalon-MM Bridge schedules
the TLP with higher priority than TX TLPs coming from the TX slave port.
Receiving a Completion TLP
The Completion TLPs associated with the Non-Posted TX requests are stored in the
RP_RX_CPL FIFO buffer and subsequently loaded into RP_RXCPL registers. The
Application Layer performs the following sequence to retrieve the TLP.
1. Polls the
RP_RXCPL_STATUS.SOP
to determine when it is set to 1’b1.
2. When
RP_RXCPL_STATUS.SOP
= 1’b’1, reads
RP_RXCPL_REG0
and
RP_RXCPL_REG1
to
retrieve dword 0 and dword 1 of the Completion TLP.
3. Read the
RP_RXCPL_STATUS.EOP.
a. If
RP_RXCPL_STATUS.EOP =
1’b0, read
RP_RXCPL_REG0
and
RP_RXCPL_REG1
to
retrieve dword 2 and dword 3 of the Completion TLP, then repeat step
.
b. If
RP_RXCPL_STATUS.EOP =
1’b1, read
RP_RXCPL_REG0
and
RP_RXCPL_REG1
to
retrieve final dwords of TLP.
PCI Express to Avalon-MM Interrupt Status and Enable Registers for Root
Ports
he Root Port supports MSI, MSI-X and legacy (INTx) interrupts. MSI and MSI-X
interrupts are memory writes from the Endpoint to the Root Port. MSI and MSI-X
requests are forwarded to the interconnect without asserting CraIrq_o.
Table 7–33
describes the
Interrupt Status
register for Root Ports. Refer to
for the definition of the
Interrupt Status
register for Endpoints.
Table 7–33. Avalon-MM Interrupt Status Registers for Root Ports (Part 1 of 2)
0x3060
Bits
Name
Access Mode
Description
[31:5]
Reserved
—
—
[4]
RPRX_CPL_RECEIVED
RW1C
Set to 1’b1 when the Root Port has received a
Completion TLP for an outstanding Non-Posted request
from the TLP Direct channel.