
130
Agere Systems Inc.
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
Data Sheet
July 2001
11 10/100 2-Port Repeater and Backplane Segment Controller
(continued)
Signal
RX_CLK(1,0)
Type
I
Description
Receive clock.
In 10 Mbits/s mode,
RX_CLK
clocks data in on
RXD[0]
. If
RXDVAV
in the
port con-
figuration register 0
is set low and once
CRS
is asserted,
RX_CLK
should not tran-
sition until valid data is placed on
RXD[0]
. If
RXDVAV
is high, a free-running
RX_CLK
can be applied to this pin because
RX_DV
will be used to qualify
RXD[0]
.
The repeater slice will not clock in
RXD[0]
when
CRS
is deasserted.
In 100 Mbits/s mode,
RX_CLK
is a 25 MHz continuous clock that provides the timing
reference for the transfer of
RX_DV
,
RXD [3:0]
, and
RX_ER
into the repeater slice.
The duty cycle of
RX_CLK
must be no worse than 35/65. When a recovered clock is
not available the source must provide a nominal 25 MHz clock. The PHY must guar-
antee that the minimum high and low times of
RX_CLK
will be 35% of the nominal
period under all conditions, including switching between recovered clock and nominal
clock. This means narrow clock slivers must never be applied to
RX_CLK
.
Receive error.
RX_ER(1,0)
I
In 10 Mbits/s mode,
RX_ER
is ignored.
In 100 Mbits/s mode,
RX_ER
indicates the PHY has determined an error condition in
the current frame.
RX_ER
must transition synchronously to
RX_CLK
. When
RX_DV
= 0,
RX_ER
= 1, and
RXD[3:0]
= 1110 is received, a false carrier is indi-
cated. The false carrier is used by the carrier integrity state machine per 27.3.1.5.1 of
IEEE
802.3 when it is enabled via the
CIMD
bit of each
port configuration register
.
Collision detect.
COL(1,0)
I
In 100 Mbits/s and 10 Mbits/s modes,
COL
must be asserted by the attached PHY to
signal a collision on the medium and must remain asserted while the collision condi-
tion exists.
COL
can be asynchronously applied to the repeater slice.
Carrier sense.
CRS
must be asserted by the attached PHY when the receive
medium is nonidle.
CRS
shall be deasserted when the receive medium has gone
idle. The PHY must ensure that
CRS
remains asserted throughout the duration of a
collision condition. The repeater slice will blind the
CRS
loopback energy from the
PHY for 16 bit times in 100 Mbits/s mode and 4 bit times in 10 Mbits/s mode.
Transmit data.
CRS(1,0)
I
TXD(1,0)[3:0]
O
In 10 Mbits/s mode,
TXD[0]
is the serial transmit data to the PHY and is clocked out
on the rising edge of
TX_CLK
. An alternate clocking scheme does not exist for
10 Mbits/s mode.
In 100 Mbits/s mode,
TXD[3:0]
represent the 4-bit data to be transmitted by the PHY.
TX_EN
will be asserted when data is to be transferred.
TXD
is clocked out of the
repeater slice with
TX_CLK
. Alternatively, if
TXCPIN
is set low in the
global config-
uration register
(see Table 115 on page 135)
, data is clocked out with an internal
25 MHz clock.
Transmit clock. Transmit data clock is a continuously running clock source by the
attached PHY.
TX_CLK(1,0)
I
TX_CLK
must be 25 MHz in 100 Mbits/s mode and 10 MHz in 100 Mbits/s mode.
This pin is ignored if
TXCPIN
= low in the
global configuration register
(see Table
115 on page 135)
.
Table 110. Repeater Slice Interface
(continued)