am79c940 Advanced Micro Devices, am79c940 Datasheet - Page 23

• Manufacturer Part Number: am79c940
• Description: Media Access Controller For Ethernet Mace
• Manufacturer: Advanced Micro Devices

CLSN
Collision (Input/Output)
An external indication that a collision condition has been
detected by the (internal or external) Medium Attach-
ment Unit (MAU), and that signals from two or more
nodes are present on the network. When the AUI port is
selected (PORTSEL [1–0] = 00), CLSN will be activated
when the CI input pair is receiving a collision indication
from the external transceiver. CLSN will be asserted
high for the entire duration of the collision detection, but
will not be asserted during the SQE Test message fol-
lowing a transmit message on the AUI. When the
10BASE-T port is selected (PORTSEL [1–0] = 01),
CLSN will be asserted high when simultaneous transmit
and receive activity is detected (logically detected when
TXD /TXP and RXD are both active). When the DAI
port is selected (PORTSEL [1–0] = 10), CLSN will be as-
serted high when simultaneous transmit and receive ac-
tivity is detected (logically detected when RXCRS and
TXEN are both active). When the GPSI port is selected
(PORTSEL [1–0] = 11), an input from the external
Manchester encoder/decoder signaling the MACE de-
vice that a collision condition has been detected on the
network, and any receive frame in progress should be
aborted.
Notes:
1. PORTSEL [1–0] and ENPLSIO are located in the PLS Configuration Control register (REG ADDR 14).
2. This pin should be externally terminated, if unused, to reduce power consumption.
Notes:
1. PORTSEL [1–0] and ENPLSIO are located in the PLS Configuration Control register (REG ADDR 14).
2. This pin should be externally terminated, if unused, to reduce power consumption.
SLEEP
SLEEP
0
1
1
1
1
1
0
1
1
1
1
1
PORTSEL
PORTSEL
[1–0]
[1–0]
XX
XX
XX
XX
00
01
10
11
00
01
10
11
ENPLSIO
ENPLSIO
X
X
1
1
1
1
0
1
1
1
1
0
STDCLK Configuration
CLSN Configuration
Am79C940
Interface Description
Interface Description
Sleep Mode
AUI
10BASE-T
DAI Port
GPSI
Status Disabled
Sleep Mode
AUI
10BASE-T
DAI Port
GPSI
Status Disabled
External Address Detection Interface
(EADI )
SF/BD
Start Frame/Byte Delimiter (Output)
The external indication that a start of frame delimiter has
been received. The serial bit stream will follow on the
Serial Receive Data pin (SRD), commencing with the
destination address field. SF/BD will go high for 4 bit
times (400 ns) after detecting the second 1 in the SFD of
a received frame. SF/BD will subsequently toggle every
400 ns (1.25 MHz frequency) with the rising edge indi-
cating the start (first bit) in each subsequent byte of the
received serial bit stream. SF/BD will be inactive during
frame transmission.
SRD
Serial Receive Data (Output)
SRD is the decoded NRZ data from the network. It is
available for external address detection. Note that when
the 10BASE-T port is selected, transition on SRD will
only occur during receive activity. When the AUI or DAI
port is selected, transition on SRD will occur during both
transmit and receive activity.
High Impedance
STDCLK Output
STDCLK Output
STDCLK Output
STDCLK Input
High Impedance (Note 2)
High Impedance
CLSN Output
CLSN Output
CLSN Output
CLSN Input
High Impedance (Note 2)
Pin Function
Pin Function
AMD
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