TXC-06885BIOG Transwitch Corporation, TXC-06885BIOG Datasheet - Page 71

• Manufacturer Part Number: TXC-06885BIOG
• Manufacturer: Transwitch Corporation

Specifications of TXC-06885BIOG

• Operating Supply Voltage (typ): 1.8/3.3V
• Operating Temperature Classification: Industrial
• Package Type: BGA
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Not Compliant

PRELIMINARY TXC-06885-MB, Ed. 6A
February 2005
Preamble
(7 bytes)
6.2.2 Egress FIFO Operations
6.2.1.3 Input SPI-3 Interface Frame Format:
6.2.2.1 Egress FIFO Write:
The Data format accepted by Envoy-CE4, at the SPI-3 Input interface, is an Ethernet frame
(VLAN frames also), excluding the preamble and the Start of frame delimiter. If the Transmit
MAC is configured to generate the Frame Check Sequence (FCS), then the FCS is optional for
the frame received by the Envoy-CE4 at the SPI-3 interface. If the Transmit MAC is not
configured to generate the FCS, then the FCS needs to be included in the frame.
Standard Ethernet Frame at SMII/GMII Transmit interface
Frame format at the SPI-3 Input Interface with Frame Check Sequence
Frame format at the SPI-3 Input Interface without Frame Check Sequence
VLAN Tagged and Extended frames may have the FCS included depending whether Envoy-
CE4 is configured to generate FCS or not.
Each Egress FIFO is 3.2 KBytes deep in SMII mode, 32 KBytes deep in GMII mode, and 12.4
KBytes deep in extended SMII mode. The Link or PHY layer device (depending on the mode
the Envoy-CE4 is in) is responsible for selecting the channel into which the frame data is
written. The Egress FIFO backpressures the SPI-3 input interface when the FIFO becomes
near full. The near full indication level is programmable as number of bytes from the FIFO full.
If the Link or PHY layer device attempts to overflow the Egress FIFO when it is configured in
Store and Forward mode, the complete frames being received are discarded and a count of
the discarded frames are provided per channel. If the Link or PHY layer device attempts to
overflow the Egress FIFO when it is configured in Streaming mode, the current frame being
received is truncated and will be sent out the targeted Ethernet port as an errored frames. All
subsequently arriving frames are discarded until some room is freed up in the Egress FIFO
and a count of the discarded frames are provided per channel.
Note: The discard frame count is used to count frames discarded due to an Egress FIFO
overflow condition and the SPI-3 Error pin assertion condition.
Delimiter
(1 byte)
Start of
Frame
Destination
(6 bytes)
Address
Destination
(6 bytes)
Address
(6 bytes)
Address
Destination
Source
- Operation -
(6 bytes)
Address
(6 bytes)
Address
Source
Length/Type
(2 bytes)
(6 bytes)
Address
Source
Length/Type
(2 bytes)
(46 to 1500 bytes)
Length/Type
(2 bytes)
Data
(46 to 1500
bytes)
Data
Envoy-CE4 Device
(46 to 1500 bytes)
Frame Check
DATA SHEET
Sequence
Data
Sequence
(4 bytes)
(4 bytes)
TXC-06885
Frame
Check
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