TXC-06880BIOG Transwitch Corporation, TXC-06880BIOG Datasheet - Page 62

• Manufacturer Part Number: TXC-06880BIOG
• Manufacturer: Transwitch Corporation

Specifications of TXC-06880BIOG

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

Envoy-CE2 Device
DATA SHEET
TXC-06880
6 2 o f 12 2
Destination Address
6.1.5 SPI-3 Output Operations
Preamble
(7 bytes)
6.1.5.1 Data Flow Operations:
6.1.5.2 SPI-3 Output Interface Frame Format:
(6 bytes)
Frames from the Ingress FIFO are read out by the Output SPI-3 interface. The interface is
programmable in either PHY or Link layer mode. The OIF System Packet Interface Level 3
(SPI-3) specification describes the interface in detail. When the SPI-3 output interface is
configured in PHY layer mode, the Link layer device performs flow control by controlling the
Read Enable. When the SPI-3 output interface is configured in Link layer mode, the PHY
layer device provides backpressure information via the Transmit Packet Available pins and
the device provides flow control using the Transmit Enable pins. The channel selection in
both PHY and Link layer modes is done by the Envoy-CE2. Once a channel has data
available for transfer based on store and forward or streaming mode, the scheduler in the
SPI-3 interface block selects the channel for frame transfer. The Envoy-CE2 provides the
burst mode option to restrict a channel from transmitting more than a fixed number of bytes
once selected. Once a burst of data bytes has been transmitted by the selected channel, a
new channel is selected for frame transfer. This prevents a channel from using up all the
bandwidth on the SPI-3 interface, by giving the other channels access to the SPI-3 interface.
The allowable burst sizes are 1 to 255 in units of 8 byte words. Alternatively, in packet transfer
mode, a complete frame is transferred across the SPI-3 interface.
Data at the SPI-3 output interface is an Ethernet frame (VLAN frames also), excluding the
preamble and start of frame delimiter. The FCS may be programmed to be excluded.
Note: The following figures show the inclusion of the FCS.
Standard Ethernet Frame at SMII/GMII interface
Frame format at SPI-3 Output Interface
• Streaming Mode: When a selectable fixed number of bytes have been written into the
FIFO, the frame is available for transfer. The SPI-3 interface may be configured for burst
(chunk) or packet transfer mode, when the FIFO is configured for store and forward.
Ingress FIFO, a chunk is available for transfer. The selection for streaming range from 1
to 255, in units of 8 byte words and is equal to the SPI-3 burst (chunk) size, defined for
the SPI-3 output. Hence, in streaming mode, the SPI-3 interface needs to be in burst
(chunk) transfer mode. When streaming is enabled and an end of frame is written into
the Ingress FIFO, before the selected number of (streaming) bytes have been received,
the frame data will be available for transfer across the SPI-3 interface based on the end
of frame condition. When streaming is enabled, frame errors at the SMII/GMII interface
are indicated on the SPI-3 interface during the transfer of the frame.
Start of Frame
Delimiter
(1 byte)
Source Address
(6 bytes)
Destination
(6 bytes)
Address
-
Operation
Length/Type
(2 bytes)
(6 bytes)
Address
-
Source
(46 to 1500 bytes)
Length/Type
(2 bytes)
Data
PRELIMINARY TXC-06880-MB, Ed. 4
(46 to 1500
Frame Check Sequence
bytes)
Data
(4 bytes)
Frame Check
Sequence
February 2005
(4 bytes)