DP83916 datasheet(11/96 Pages) NSC

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10 Functional Description (Continued)

TABLE 1-1 Network Management Statistics

Statistic

Bits Used

Frames Transmitted OK

TCR (Note)

PTX

Single Collision Frames

(Note)

NC0 – NC4

Multiple Collision Frames

(Note)

NC0 – NC4

Collision Frames

(Note)

NC0 – NC4

Frames with Deferred Transmissions

TCR (Note)

DEF

Late Collisions

TCR (Note)

OWC

Excessive Collisions

TCR (Note)

EXC

Excessive Deferral

TCR (Note)

EXD

Internal MAC Transmit Error

TCR (Note)

BCM FU

Frames Received OK

RCR (Note)

PRX

Multicast Frames Received OK

RCR (Note)

Broadcast Frames Received OK

RCR (Note)

Frame Check Sequence Errors

CRCT

All

RCR

CRC

Alignment Errors

FAET

All

RCR

FAE

Frame Lost due to Internal MAC Receive Error

MPT

All

ISR

RFO

Note

The number of collisions and the contents of the Transmit Control register are posted in the TXpktstatus field (see

section 3512) The contents of the Receive Control register are posted in the RXpktstatus field (see section 3431)

20 TransmitReceive IEEE 8023 Frame Format

A standard IEEE 8023 packet

(Figure 2-1 ) consists of the

following fields preamble Start of Frame Delimiter (SFD)

destination address

source address

length

data and

Frame Check Sequence (FCS) The typical format is shown

Figure 2-1 The packets are Manchester encoded and

decoded by the ENDEC unit and transferred serially tofrom

the MAC unit using NRZ data with a clock All fields are of

fixed length except for the data field The SONIC-16 gener-

ates and appends the preamble SFD and FCS field during

transmission The Preamble and SFD fields are stripped

during reception (The CRC is passed through to buffer

memory during reception)

21 PREAMBLE AND START OF FRAME DELIMITER

(SFD)

The Manchester encoded alternating 10 preamble field is

used by the ENDEC to acquire bit synchronization with an

incoming packet When transmitted each packet contains

62 bits of an alternating 10 preamble Some of this pream-

ble may be lost as the packet travels through the network

Byte alignment is performed when the Start of Frame Delim-

iter (SFD) pattern consisting of two consecutive 1’s is de-

tected

22 DESTINATION ADDRESS

The destination address indicates the destination of the

packet on the network and is used to filter unwanted pack-

Note

B e bytes

b e bits

TLF11722 – 9

FIGURE 2-1 IEEE 8023 Packet Structure

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