DP83959 datasheet(18/38 Pages) NSC

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5.0

Functional Description (Continued)

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5.11

PORT STATUS LEDS

The eight 10BASE-T Port Partition Status/Link OK Status

bi-color LED outputs have the functionality given in Table 2.

The representational logic of this function is given in

Figure 6. This logic is repeated for each of the 10BASE-T

ports ('n' in Figure 6 refers to any of ports 1 through 8). The

DP83959 bi-color LED outputs use two pins each, so that ei-

ther end of a two-lead bi-color LED may be driven high or

low in order to achieve the required functionality. Two-lead

bi-color LEDs require only the addition of a single series cur-

rent limiting resistors. Three lead bi-color LEDs must be

driven with two series resistors (one in each cathode lead)

and the common anode lead taken to VCC.

If required, single LEDs may be driven by the bi-color out-

puts (each taken to VCC via an appropriate resistor).

Figure 5 shows one conﬁguration, using bi-color LEDs.

5.12

CONFIGURATION/REGISTER INTERFACE

Several operational parameters can be conﬁgured into the

LERIC8 at power-on/reset time (optional mode) or the stan-

dard LERIC8 conﬁguration can be used (default mode). Se-

lection of the mode is made using the DEF/OPT pin.

For default mode, the DEF/OPT pin must be pulled high (to

VCC) with a 4.7 kΩ resistor. In this mode, the LERIC8 uses

the default values given in Table 3.

For optional mode, the DEF/OPT pin must be pulled low. In

this mode, the rising edge of either the internal reset signal

or /MLOAD (see Section 5.9) is used to latch the logic levels

held on the D[3:0] and RA[4:0] inputs into the internal con-

ﬁguration registers. Conﬁguration data is set on the D[3:0]

and RA[4:0] pins using 10 k

Ω pull-up or pull-down resistors

as required. Table 3 shows the parameter sections possible.

A 10 k

Ω pull-up resistor to VCC is required to set a conﬁgu-

ration bit to 1. A 10 k

Ω pull-down resistor to GND to set a

conﬁguration bit to 0.

The LERIC8 has internal registers that are accessible from

the RA[4:0] and D[3:0] interface. A certain amount of control

of operation and status information is available through this

interface. The LERIC8's registers are compatible with those

in the DP83955/6. A full description of the registers is given

in Section 6.0.

Although simple 8-port standalone hubs will not require the

sary factory test feature. In a simple repeater design the /RD

and /WR pins should be disabled by connecting them to

VCC directly or via a suitable pull-up resistor (4.7 k

Ω).

Since the RA[4:0] and D[3:0] interface is used for multiple

functions (conﬁguration, register access and Min/Max LED

mode outputs) register read/write data must be transferred

using an external buffer.

The READY pin provides a means of handshaking register

accesses into the LERIC8. A simple programmable logic de-

vice (GAL) may be used to decode the address range, as-

sert the appropriate /RD or /WR strobe and check the

READY signal. This provides an appropriate interface for

whatever CPU or other device is connected.

Table 2

10BASE-T Port Status LED Output Functionality Using Bi-color LEDs

Link Status

Port Partition Status

LED

Not OK

Not Partitioned

OFF

Not OK

Partitioned

OFF

Not Partitioned

Color #1 (usually GREEN)

Partitioned

Color #2 (usually YELLOW or RED)

Figure 6.

10BASE-T Port Status LED Logic Function

P/L_nA

Port Partition Status (1 = Partitioned)

P/L_nB

Port Link Status (1 = Link OK)

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