DP83953 datasheet(44/90 Pages) NSC

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6.0 Port Block Functions

The RIC2A has 13 port logic blocks (one for each network

connection). In addition to the packet repetition operations

already described, the port block performs two other func-

tions:

1. the physical connection to the network segment (trans-

ceiver function).

2. it provides a means to protect the network from malfunc-

tioning segments (segment partition).

Each port has its own status register. This register allows

the user to determine the current status of the port and

configure a number of port specific functions.

6.1 Transceiver Functions

The RIC2A may connect to network segments in two ways:

1. over AUI cable to transceiver boxes,

2. to twisted pair cable via a simple interface.

The first method is only supported by RIC2A port 1 (the

AUI port). Twisted pair cable connection, (2), is only sup-

ported on ports 2 to 13.

10BASE-T Transceiver Operation

The RIC2A contains virtually all of the digital and analog

circuitry required for connection to 10BASE-T network seg-

ments. The RIC2A design even integrates transmit filters.

The Figure 16 shows the connection for a RIC2A port to a

10BASE-T segment

The operation of the 10BASE-T transceiver's logical func-

tions may be modified by software control. The default

operation allows the transceivers to transmit and expect

reception of link pulses. If the designer writes a logical one

to the GDLNK bit of a port's status register, the default

mode may be modified. The port's transceiver will operate

normally but will not transmit link pulses or monitor their

reception. Therefore, a link fail state and the associated

modification of transceiver operation will not occur.

The on-chip 10BASE-T transceivers automatically detects

and correct the polarity of the received data stream. This

polarity detection scheme relies upon the polarity of the

received link pulses and the end of packet waveform. Polar-

ity detection and correction may be disabled by software

control.

Figure 16. Port Connection to a 10BASE-T Segment

Pre-emphasis resistor network/filters and per port buffer/driver are all integrated in the RIC2A.

Where C = 0.01

µF, C1 = 1.0 nF, R2 = 49.9Ω, and R1 =10Ω. All values are typical and ± 1%.

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