TXC-06885BIOG Transwitch Corporation, TXC-06885BIOG Datasheet - Page 75

• 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
OPERATIONAL
AGGREGATE
NORMAL
6.4 ETHERNET HALF DUPLEX
MODE
6.3.1 Normal vs. Aggregate Mode
6.4.1 Overview
6.4.2 Carrier Sense
6.4.3 Collision Detection
* Note: The single port is either in Multi-PHY or Single-PHY mode.
In Half-Duplex mode, two or more Ethernet devices are connected to a common transmission
medium and when one Ethernet device transmits, the others listen. In the case where two
Ethernet devices transmit at once, a “Collision” is said to have occurred. A “Jam Sequence” is
transmitted by the transmitting Ethernet device indicating the occurrence of a collision. The
contention is resolved by each of the Ethernet devices responsible for the collision, backing
off, and attempting to re-transmit after a time period. This method is called Carrier Sense
Multiple Access/Collision Detection (CSMA/CD). The Envoy-CE4 Configurable Media Access
Controller implements the IEEE 802.3 compliant CSMA/CD algorithm. For a complete
definition of this algorithm, please refer to the IEEE 802.3 specification.
Note: Carrier Sense and Collision detection status is indicated by the Ethernet PHY device to
Following is an outline based on the Envoy-CE4 Configurable MAC.
Following the transmission of an Ethernet frame from the Envoy-CE4, the MAC times the
Inter Packet Gap (IPG) count as programmed in the Back-to-Back IPG configuration register
for the specific port. The MAC monitors the Carrier Sense status for the duration of IPG time
before transmitting a new frame for the port. Envoy-CE4 provides an optional IPG mechanism
where the IPG time is divided into a two-thirds/one-third ratio. During the first two-thirds of the
IPG, the IPG timer is reset and Carrier Sense status is monitored or sensed. During the final
one-third of the IPG, the Carrier sense status is ignored and the port begins transmission
once the IPG timer has expired. This optional mechanism enhances system robustness. The
configuration bits defining the two-thirds/one-third values are IPG1 and IPG2.
In the event the Envoy-CE4 MAC detects a collision for a port when the device is transmitting
an Ethernet frame, the MAC outputs the 32-bit jam sequence for the port. The jam sequence
is made up of several bits of the CRC, inverted to guarantee an invalid CRC upon reception of
the frame. The port then backs off transmission of the frame (retry) based on the “Truncated
Binary Exponential Backoff” (BEB) algorithm. Following this backoff time, the frame is retried.
When enabled, the “No Backoff” configuration bit (Register 0x400C Bit 17) retransmits the
frame without a backoff, following a collision. This option needs to be enabled with caution.
Default
Yes
the Envoy-CE4 via the SMII and MII interface only. Please refer to the Serial Media
Independent Interface (SMII) specification for further details.
No
Backpressure
Port SPI-3 Tx
Per Ethernet
Yes
No
- Operation -
Tagging
Packet/
Chunk
Yes
No
PAUSE Frame
Ethernet Port
support per
Yes
Yes
Chunking
SPI-3
Yes
Yes
Envoy-CE4 Device
SPI-3 Ports
DATA SHEET
Number of
supported
Multiple
Single*
TXC-06885
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