Altera Stratix V Avalon-ST User Manual
Page 39
Table 4-2: Component Specific TX Credit Signals
Signal
Direction
Description
tx_cred_
datafccp[11:0]
Output
Data credit limit for the received FC completions. Each credit is
16 bytes.
tx_cred_
datafcnp[11:0]
Output
Data credit limit for the non-posted requests. Each credit is 16
bytes.
tx_cred_datafcp[11:0]
Output
Data credit limit for the FC posted writes. Each credit is 16 bytes.
tx_cred_
fchipcons[5:0]
Output
Asserted for 1 cycle each time the Hard IP consumes a credit.
These credits are from messages that the Hard IP for PCIe
generates for the following reasons:
• To respond to memory read requests
• To send error messages
This signal is not asserted when an Application Layer credit is
consumed. The Application Layer must keep track of its own
consumed credits. To calculate the total credits consumed, the
Application Layer must add its own credits consumed to those
consumed by the Hard IP for PCIe. The credit signals are valid
after
dlup
(data link up) is asserted.
The 6 bits of this vector correspond to the following 6 types of
credit types:
• [5]: posted headers
• [4]: posted data
• [3]: non-posted header
• [2]: non-posted data
• [1]: completion header
• [0]: completion data
During a single cycle, the IP core can consume either a single
header credit or both a header and a data credit.
tx_cred_fc_
infinite[5:0]
Output
When asserted, indicates that the corresponding credit type has
infinite credits available and does not need to calculate credit
limits. The 6 bits of this vector correspond to the following 6
types of credit types:
• [5]: posted headers
• [4]: posted data
• [3]: non-posted header
• [2]: non-posted data
• [1]: completion header
• [0]: completion data
4-4
Avalon-ST TX Interface
UG-01097_sriov
2014.12.15
Altera Corporation
Interfaces and Signal Descriptions