DP83950BVQB National Semiconductor, DP83950BVQB Datasheet - Page 50

• Manufacturer Part Number: DP83950BVQB
• Description: IC CTRLR RIC REPEATER 160-PQFP
• Manufacturer: National Semiconductor

Specifications of DP83950BVQB

• Controller Type: Ethernet Repeater Interface Controller
• Interface: IEEE 802.3
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 380mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-MQFP, 160-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *DP83950BVQB

7 0 Port Block Functions
7 1 TRANSCEIVER FUNCTIONS
The RIC may connect to network segments in three ways
1 Over AUI cable to transceiver boxes
2 Directly to board mounted transceivers
3 To twisted pair cable via a simple interface
The first method is only supported by RIC port 1 (the AUI
port) Options (2) and (3) are available on ports 2 to 13 The
selection of the desired option is made at device initializa-
tion during the Mode Load operation The Transceiver By-
pass XBYPAS configuration bits are used to determine
whether the ports will utilize the on-chip 10BASE-T trans-
ceiver or bypass these in favour of external transceivers
Four possible combinations of port utilization are supported
All ports (2 to 13) use the external Transceiver Interface
Ports 2 to 5 use the external interface 6 to 13 use the
internal 10BASE-T transceivers
Ports 2 to 7 use the external interface 8 to 13 use the
internal 10BASE-T transceivers
All ports (2 to 13) use the internal 10BASE-T transceivers
10BASE-T Transceiver Operation
The RIC contains virtually all the digital and analog circuits
required for connection to 10BASE-T network segments
The only additional active component is an external driver
packet The connection for a RIC port to a 10BASE-T seg-
ment is shown in Figure 7 1 The diagram shows the compo-
nents required to connect one of the RIC’s ports to a
10BASE-T segment The major components are the driver
package a member of the 74ACT family and an integrated
filter choke network
The operation of the 10BASE-T transceiver’s logical func-
tions may be modified by software control The default
mode of operation is for the transceivers to transmit and
expect reception of link pulses This may be modified if a
logic one is written to the GDLNK bit of a port’s status regis-
ter The port’s transceiver will operate normally but will not
transmit link pulses nor monitor their reception Thus the
entry to a link fail state and the associated modification of
transceiver operation will not occur
The on-chip 10BASE-T transceivers automatically detect
and correct the polarity of the received data stream This
polarity detection scheme relies upon the polarity of the re-
ceived link pulses and the end of the packet waveform Po-
larity detection and correction may be disabled under soft-
ware control as follows
1) Write the value 07H to the Page Select Register (address
2) Write the value 02H to the address 11H (Note that ad-
This is the only exception for accessing any of the reserved
pages 4 to 7
External Transceiver Operation
RIC ports 2 to 13 may be connected to media other than
twisted-pair by opting to bypass the on-chip transceivers
When using external transceivers the user must have the
external transceivers perform collision detection and the
other functions associated with an IEEE 802 2 Media Ac-
cess Unit Figure 7 2 shows the connection between a re-
peater port and a coaxial transceiver using the AUI type
interface
10H)
dress 11H will read back 00H after writing 02H to it)
(Continued)
50
7 2 SEGMENT PARTITION
Each of the RIC’s ports has a dedicated state machine to
perform the functions defined by the IEEE partition algo-
rithm as shown in Figure 7 3 To allow users to customize
this algorithm for different applications a number of user
selected options are available during device configuration at
power up (the Mode Load Cycle)
Five different options are provided
1 Operation of the 13 partition state machines may be dis-
2 The value of consecutive counts required to partition a
3 The use of the TW5 specification in the partition algorithm
4 The operation of the ports’ state machines when recon-
5 The RIC may be configured to use an additional criterion
In addition to the autonomous operation of the partition
state machines the user may reset these state machines
This may be done individually to each port by writing a logic
one to the PART bit in its status register The port’s partition
state machine and associated counters are reset and the
port is reconnected to the network The reason why a port
become partitioned may be discovered by the user by read-
ing the port’s status register
abled via the disable partition DPART configuration bit
(Pin D6)
segment (the CCLimit specification) may be set at either
31 or 63 consecutive collisions
differentiates between collisions which occur early in a
packet (before TW5 has elapsed) and those which occur
late in the packet (after TW5 has elapsed) These late or
‘‘out of window’’ collisions can be regarded in the same
manner as early collisions if the Out of Window Collision
Enable OWCE option is selected This configuration bit is
applied to the D4 pin during the Mode Load operation
The use of OWCE delays until the end of the packet the
operation of the state diagram branch marked (1) and
enables the branch marked (2) in Figure 7 3
necting a segment may also be modified by the user The
Transmit Only TXONLY configuration bit allows the user
to prevent segment reconnection unless the reconnect-
ing packet is being sourced by the repeater In this case
the repeater is transmitting on to the segment rather
than the segment transmitting when the repeater is idle
The normal mode of reconnection does not differentiate
between such packets The TXONLY configuration bit is
input on Pin D5 during the Mode Load cycle If this option
is selected the operation of the state machine branch
marked (3) in Figure 7 3 is affected
for segment partition This is referred to as loop back
partition If this operation is selected the partition state
machine monitors the receive and collision inputs from a
network segment to discover if they are active when the
port is transmitting Thus determining if the network trans-
ceiver is looping back the data pattern from the cable A
port may be partitioned if no data or collision signals are
seen by the partition logic in the following window 61 to
96 network bit times after the start of transmission see
data sheet Section 8 for details A segment partitioned by
this operation may be reconnected in the normal manner