Intel NETWORK PROCESSOR IXP2800 - Manual (Page 277)

Hardware Reference Manual 277
Intel
®
IXP2800 Network Processor
Media and Switch Fabric Interface
8.5.2.1 Full Duplex CSIX
In Full Duplex Mode, the information from the Switch Fabric is sent to the Egress IXP2800
Network Processor and must be communicated to the Ingress IXP2800 Network Processor via
TXCSRB or RXCSRB. CSIX CFrames received from the Switch Fabric on the Egress IXP2800
Network Processor are put into FCEFIFO, based on the mapping in the CSIX_Type_Map CSR
(normally they will be the Flow Control CFrames). The entire CFrame is put in, including the Base
Header and Vertical Parity field.
The CFrames are forwarded in a “cut-through” manner, meaning the Egress IXP2800 Network
Processor does not wait for the entire CFrame to be received before forwarding. The Egress
processor will corrupt the Vertical Parity of the CFrame being forwarded if either a Horizontal or
Vertical Parity is detected during receive, to inform the Ingress processor that an error occured.The
Ingress IXP2800 Network Processor checks both Horizontal Parity and Vertical Parity and will
discard the entire CFrame if bad parity is detected. The signal protocol details of how the
information is sent from the Egress IXP2800 Network Processor to the Ingress IXP2800 Network
Processor is described in
Section 8.5.3 . (See Figure 98 .)
The Ingress IXP2800 Network Processor puts the CFrames into the FCIFIFO, including the Base
Header and Vertical Parity fields. It does not make a CFrame visible in the FCIFIFO until the entire
CFrame has been received without errors. If there is an error, the entire CFrame is discarded and
MSF_Interrupt_Status[FCIFIFO_Error] is set.
CFrames in the FCIFIFO of the Ingress IXP2800 Network Processor are read by Microengines,
which use them to keep current VOQ Flow Control information. (The application software
determines how and where that information is stored and used.)
Figure 98. CSIX Flow Control Interface — FCIFIFO and FCEFIFO in Full Duplex Mode
A9763-01
TDAT
RXCSRB
TXCSRB
RXCDAT, RXCPAR, RXCSOF
TXCDAT, TXCPAR, TXCSOF
RXCFC
TXCFC
RDAT
Ingress
Intel
® IXP2800
Network Processor
Egress
Intel
® IXP2800
Network Processor
Switch
Fabric
msf[read]
FCI_Not_Empty
FCI_Full
FCIFIFO
FCEFIFO
MSF_Rx_Control[Duplex_Mode]
From MEs
To MEs