DP83916 datasheet(7/96 Pages) NSC

7 / 96 page

10 Functional Description (Continued)

Serializer

After data has been written into the 32-byte

transmit FIFO the serializer reads byte wide data from the

FIFO and sends a NRZ data stream to the Manchester en-

coder The rate at which data is transmitted is determined

by the transmit clock (TXC) The serialized data is transmit-

ted after the SFD

Preamble Generator

The preamble generator prefixes a

62-bit alternating ‘‘10’’ pattern and a 2-bit ‘‘11’’ SFD pat-

tern at the beginning of each packet This allows receiving

nodes to synchronize to the incoming data The preamble is

always transmitted in its entirety even in the event of a colli-

sion This assures that the minimum collision fragment is 96

bits (64 bits of normal preamble and 4 bytes or rather 32

bits of the JAM pattern)

CRC Generator

The CRC generator calculates the 4-byte

FCS field from the transmitted serial data stream If en-

abled the 4-byte FCS field is appended to the end of the

transmitted packet (section 26)

Jam Generator

The Jam generator produces a 4-byte pat-

tern of all 1’s to assure that all nodes on the network sense

the collision When a collision occurs the SONIC-16 stops

transmitting data and enables the Jam generator If a colli-

sion occurs during the preamble the SONIC-16 finishes

transmitting the preamble before enabling the Jam genera-

tor (see Preamble Generator above)

13 BYTE ORDERING

The SONIC-16 will operate with 16-bit wide memory The

SONIC-16 provides both Little Endian and Big Endian byte-

ordering capability for compatibility with NationalIntel or

Motorola microprocessors respectively by selecting the

proper level on the BMODE pin The byte ordering is depict-

ed as follows

Little Endian mode (BMODE e 0)

The byte orientation for

received and transmitted data in the Receive Buffer Area

(RBA) and Transmit Buffer Area (TBA) of system memory is

as follows

16-Bit Word

Byte 1

Byte 0

MSB

LSB

Big Endian mode (BMODE e 1)

The byte orientation for

received and transmitted data in the RBA and TBA is as

follows

16-Bit Word

Byte 0

Byte 1

LSB

MSB

TLF11722 – 6

FIGURE 1-5 Receive FIFO

DP83916 датащи(PDF) 7 Page - National Semiconductor (TI)

DP83916 датащи(HTML) 7 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

датащи скачать

ссылки URL