Receive Credit Limit Register 0 VC0 @0xc

This register contains the initial credit limits advertised by the Controller during th DL initialization. If the fields of this register are modified, the link must be re-trained to re-initialize the DL for the modified settings to take effect. The credit limit fields in this register can be programmed to any value lesser than or equal to the respective default values. The default values are set to advertise the full size of the receive buffers. If a value of 0x00 is programmed, it implies infinite credit. Note: This may result in receiver overflow if received data is back pressured on the Client interface.

Table 1. i_rcv_cred_lim_0_reg
Bits SW Name Description Reset
11:0 R/W Posted Payload Credit VC0 [PPC] Posted payload credit limit advertised by the Controller for VC 0. This field is in units of four DWords, 16 DWords, or 64 DWords based on the Local Posted Payload Credit Scale for VC 0.
  • 00b => (units of four DWords),
  • 01b => (units of four DWords),
  • 10b => (units of 16 DWords),
  • 11b => (units of 64 DWords).
Note:When Scaled FLow Control is Activated, the programmed credit value is advertised in the InitFC DLLPs. Else, the programmed credit value is internally normalized to units of four DW and then advertised in the InitFC DLLPs.
Caution: The programmed Header and Payload credit values must not exceed the actual size of the Receive Buffer.
 0x0f8
19:12 R/W Posted Header Credit VC0 [PHC] Posted header credit limit advertised by the Controller for VC 0. This field is in units of one, four, or 16 Packet Headers based on the Local Posted Header Credit Scale for VC 0.
  • 00b => (units of one Packet Header),
  • 01b => (units of one Packet Header),
  • 10b => (units of four Packet Headers),
  • 11b => (units of 16 Packet Headers).
Note:When Scaled Flow Control is Activated, the programmed credit value is advertised in the InitFC DLLPs. Else, the programmed credit value is internally normalized to units of (one Packet Header) and then advertised in the InitFC DLLPs.
Note: Packet Header represents one maximum-size TLP Header + TLP Digest + maximum number of End-End TLP Prefixes permitted in a TLP.
Caution: The programmed Header and Payload credit values must not exceed the actual size of the Receive Buffer.
 0x20
31:20 R/W Non-Posted Payload Credit VC0 [NPPC] Non-Posted payload credit limit advertised by the Controller for VC 0. This field is in units of four DWords, 16 DWords or 64 DWords based on the Local Posted Payload Credit Scale for VC 0.
  • 00b => (units of four DWords),
  • 01b => (units of four DWords),
  • 10b => (units of 16 DWords),
  • 11b => (units of 64 DWords).
Note:When Scaled FLow Control is Activated, the programmed credit value is advertised in the InitFC DLLPs. Else, the programmed credit value is internally normalized to units of four DW and then advertised in the InitFC DLLPs.
Caution: The programmed Header and Payload credit values must not exceed the actual size of the Receive Buffer.
 0x20