AM79C985KCW AMD [Advanced Micro Devices], AM79C985KCW Datasheet - Page 12

• Manufacturer Part Number: AM79C985KCW
• Manufacturer: AMD [Advanced Micro Devices]

PIN DESCRIPTION
AUI Port
DI+, DI–
Data In
Differential Input
DI
signals comply with IEEE 802.3, Section 7.
DO+, DO–
Data Out
Differential Output
DO are differential, Manchester output driver pins. The
signals comply with IEEE 802.3, Section 7.
CI+, CI–
Collision Input
Differential Input/Output
CI are differential, Manchester I/O signals. As an input,
CI is a collision-receive indicator. As an output, CI gen-
erates a 10-MHz signal if the eIMR+ device senses a
collision.
Twisted Pair Ports
TXD+
Transmit Data
Differential Output
TXD are 10BASE-T port differential drivers (4 ports).
RXD+
Receive Data
Differential Input
RXD are 10BASE-T port differential receive inputs
(4 ports).
Expansion Bus
DAT
Data
Input/Output/3-State
If the SELO and ACK pins are asserted during non-
collision conditions, the eIMR+ device drives NRZ data
onto the DAT line, regenerating the preamble if neces-
sary. During a collision, when JAM is HIGH, DAT is used
to differentiate between single-port (DAT=1) and multi-
port (DAT=0) collisions. DAT is an output when ACK is
asserted and the eIMR+ device’s ports are active; DAT
is an input when ACK is asserted and the ports are
inactive. If ACK is not asserted, DAT is in the high-im-
pedance state. It is recommended that DAT be pulled
up or down via a high value resistor.
JAM
Jam
Input/Output/3-State
The active eIMR+ device drives JAM HIGH, if it detects
a collision condition on one or more of its ports. The
12
are differential, Manchester receiver pins. The
0-3
0-3
, TXD–
, RXD–
0-3
0-3
P R E L I M I N A R Y
Am79C985
state of the DAT pin is used in conjunction with JAM to
indicate a single port (DAT =1) or multiport (DAT=0) col-
lision. JAM is in the high-impedance state if neither the
SEL nor ACK signal is asserted. It is recommended that
JAM be pulled up or down via a high value resistor.
SELI
Select In
Input, Active LOW
When the expansion bus is configured for Internal Arbi-
tration mode, these signals indicate that another eIMR+
device is active; SELI
the upstream device. At reset, SELI
the Internal Arbitration mode and the IMR+ mode of the
expansion bus; a HIGH selects the Internal Arbitration
mode and a LOW selects the IMR+ mode.
SELO
Select Out
Output, Active LOW
If the expansion bus is configured for Internal Arbitration
mode, an eIMR+ device drives this pin LOW when it is
active or when either of its SELI
active eIMR+ device is defined as having one or more
ports receiving or colliding and/or is still transmitting
data from the internal FIFO, or extending a packet to the
minimum of 96 bit times. When the expansion bus is
configured for IMR+ mode, SELO is active when the
eIMR+ device is active (acquiring the functionality of the
REQ pin on the Am79C981 IMR+ device).
ACK
Acknowledge
Input/Output, Active LOW, Open Drain
This signal is asserted to indicate that an eIMR+ device
is active. It also signals to the other eIMR+ devices the
presence of a valid collision status on the JAM line and
valid data on the DAT line. When the eIMR+ device is
configured for Internal Arbitration mode, ACK is an I/O,
and must be pulled to VDD via a minimum equivalent
resistance of 1 k When the eIMR+ device is configured
for IMR+ mode, ACK is an input driven by an external
arbiter.
COL
Collision
Input/Output, Active LOW, Open Drain
When asserted, COL indicates that more than one
eIMR+ device is active. Each eIMR+ device generates
the Collision Jam sequence independently. When the
eIMR+ device is configured for Internal Arbitration
0-1
SELI_1
X
X
0
SELI_0
or SELI
1
0
1
is driven by SELO from
0-1
Internal
IMR+
0
Arbitration
pins is LOW. An
selects between
Mode