DP83932B datasheet(47/96 Pages) NSC

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50 Bus Interface (Continued)

TABLE 5-1 Pin Description

(Continued)

Symbol

Driver

Direction

Description

Type

NETWORK INTERFACE PINS

(Continued)

LBK

This pin will be TRI-STATE until the DCR has been written to (See Section 432

EXUSR2

TRI

O Z

EXBUS for more information)

Loopback (LBK)

When ENDEC loopback is programmed this pin is asserted high

Although this signal is used internally by the SONIC-16 it is also provided as an output to

the user

Extended User Output (EXUSR2)

When EXBUS has been set (see Section 432) this

pin becomes a programmable output It will remain TRI-STATE until the SONIC-16

becomes a bus master at which time it will be driven according to the value

programmed in the DCR2 (Section 437)

PCOMP

TRI

O Z

Packet Compression

This pin is used with the Management Bus of the DP83950

Repeater Interface Controller (RIC) The SONIC-16 can be programmed to assert

PCOMP whenever there is a CAM match or when there is not a match The RIC uses

this signal to compress (shorten) a received packet for management purposes and to

reduce memory usage (See the DP83950 datasheet for more details on the RIC

Management Bus) The operation of this pin is controlled by bits 1 and 2 in the DCR2

SEL

Mode Select

(EXT e 0) This pin is used to determine the voltage relationship between

TXa and TXb during idle at the primary of the isolation transformer on the network

interface When tied to VCC TXa and TXb are at equal voltages during idle When tied

to ground the voltage at TXa is positive with respect to TXb during idle on the primary

side of the isolation transformer (

Figure 6-2 )

PREJ

I O

Packet Reject

This signal is used to reject received packets When asserted low for at

least two receive clocks (RXC) the SONIC-16 will reject the incoming packet This pin

can be asserted up to the 2nd to the last bit of reception to reject a packet

Crystal or External Oscillator Input

This signal is used to provide clocking signals for

the internal ENDEC A crystal can be connected to this pin along with X2 or an

oscillator module may be used Typically the output of an oscillator module is connected

to this pin See Section 613 for more information about using oscillators or crystals

I O

Crystal Feedback Output

This signal is used to provide clocking signals for the

internal ENDEC A crystal may be connected to this pin along with X1 or an oscillator

module may be used See Section 613 for more information about using oscillator

modules or crystals

BUS INTERFACE PINS

BMODE

Bus Mode

This input enables the SONIC-16 to be compatible with standard

microprocessor buses The level of this pin affects byte ordering (little or big endian) and

controls the operation of the bus interface control signals A high level (tied to VCC)

selects Motorola mode (big endian) and a low level (tied to ground) selects National

Intel mode (little endian) Note the alternate pin definitions for AS ADS MRW MWR

INT INT BR HOLD BG HLDA SRW SWR DSACK0 RDYi and DSACK1 RDYo

When BMODE e 1 the first pin definition is used and when BMODE e 0 the second pin

definition is used See Sections 541 544 and 545

D31 – D0

TRI

I O Z

Data Bus

These bidirectional lines are used to transfer data on the system bus When

the SONIC-16 is a bus master 16-bit data is transferred on D15 – D0 and 32-bit data is

transferred on D31 – D0 When the SONIC-16 is accessed as a slave register data is

driven onto lines D15 – D0

DP83932B Datasheet(PDF) 47 Page - National Semiconductor (TI)

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