ADM7008
Function Description
10BASE-T RECEIVER
RXCLK
RXD
TESTMD
CRS
RXD[3:0]
RXDV
COL
RXP
RXN
RECEIVE
FILTER
SYNC
PLL CLOCK
PHASE
TXEN
TXER
10BASE-T TRANSMITTER
GENERATOR
SYNC
TXD
TXD[3:0]
TXCLK
TXP
10/100 TX
DRIVER
WAVE
SHAPER
TXN
Figure 3-3 10Base-T Block Diagram and Data Path
3.1.12 Collision Detection
The SMII does not have a collision pin. Collision is detected internal to the MAC, which
is generated by an AND function of TXEN and CRS derived from TXD and RXD,
respectively. The internal MII will still generate the COL signal, but this information is
not passed to the AMC via the SMII.
3.1.13 Jabber Function
The jabber function monitors the ADM7008 output and disables the transmitter if it
attempts to transmit a longer than legal sized packet. If TXEN is high for greater than
24ms, the 10Base-T transmitter will be disabled. Once disabled by the jabber function,
the transmitter stays disabled for the entire time that the TXEN signal is asserted. This
signal has to be deasserted for approximately 408 ms (The un-jab time) before the jabber
function re-enables the transmit outputs. The jabber function can be disabled by
programming bit 0 of register address 10h to high.
3.1.14 Link Test Function
A link pulse is used to check the integrity of the connection with the remote end. If valid
link pulses are not received, the link detector disables the 10Base-T twisted-pair
transmitter, receiver, and collision detection functions.
The link pulse generator produces pulses as defined in IEEE 802.3 10Base-T standard.
Each link pulse is nominally 100ns in duration and is transmitted every 16 ms, in the
absence of transmit data. Setting bit 10 of register 10h to high can disable link pulse
check function.
ADMtek Inc.
3-10
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