DP83907 datasheet(16/70 Pages) NSC

16 / 70 page

40 Functional Description (Continued)

TLF12082 – 8

FIGURE 13 Twisted Pair Interface Module Block Diagram

A second DMA channel (Remote DMA) is used as a slave

DMA to transfer data between the local buffer memory and

the host system The Local DMA and Remote DMA are in-

ternally arbitrated with the Local DMA channel having high-

est priority Both DMA channels use a common external bus

clock to generate all required bus timing External arbitration

is performed with a standard bus request bus acknowledge

handshake protocol

49 TWISTED PAIR INTERFACE MODULE

The TPI consists of five main logical functions

a) The ReceiverSmart Squelch responsible for determin-

ing when valid data is present on the differential receive

inputs (RXIg) and receiving the data

b) The Collision function checks for simultaneous transmis-

sion and reception of data on the TXOg and RXIg pins

c) The Link DetectorGenerator checks the integrity of the

cable connecting the two twisted pair MAUs

d) The Jabber disables the transmitter if it attempts to

transmit a longer than legal packet

e) The TX Driver and Pre-emphasis transmits Manchester

encoded data to the twisted pair network via the sum-

ming resistors and transformerfilter

DP83907 Datasheet(PDF) 16 Page - National Semiconductor (TI)