AM79C940JC/W AMD [Advanced Micro Devices], AM79C940JC/W Datasheet - Page 20

• Manufacturer Part Number: AM79C940JC/W
• Manufacturer: AMD [Advanced Micro Devices]

TXEN/TXEN
Transmit Enable (Output)
When the AUI port is selected (PORTSEL [1-0] = 00),
an output indicating that the AUI DO differential output
has valid Manchester encoded data is presented.
When the 10BASE-T port is selected (PORTSEL [1-0]
= 01), indicates that Manchester data is being output
on the TXD /TXP complementary outputs. When the
DAI port is selected (PORTSEL [1–0] = 10), indicates
that Manchester data is being output on the DAI port
TXDAT complementary outputs. When the GPSI port
is selected (PORTSEL [1–0] =11), indicates that NRZ
data is being output from the MAC core of the MACE
device, to an external Manchester encoder/decoder, on
the TXDAT+ output. Active low when the DAI port is
selected, active high when the AUI, 10 BASE-T or
GPSI is selected. Operates at TTL levels.
RXDAT
Receive Data (Input)
When the DAI port is selected (PORTSEL [1–0] = 10),
the Manchester encoded data input to the integrated
clock recovery and Manchester decoder of the MACE
device, from an external network transceiver. When the
GPSI port is selected (PORTSEL [1–0] =11), the NRZ
Notes:
1. PORTSEL [1–0] and ENPLSIO are located in the PLS Configuration Control register (REG ADDR 14).
2. When the GPSI port is selected, TXEN should have an external pull-down attached (e.g. 3.3k ) to ensure the output is held
3. This pin should be externally terminated, if unused, to reduce power consumption.
20
inactive before ENPLSIO is set.
SLEEP
0
1
1
1
1
1
PORTSEL
[1-0]
XX
XX
00
01
10
11
ENDPLSIO
TXEN/TXEN Configuration
X
1
1
1
1
0
Am79C940
Sleep Mode
AUI
10BASE-T
DAI Port
GPSI
Status Disabled
Interface Description
decoded data input to the MAC core of the MACE
device, from an external Manchester encoder/decoder.
Operates at TTL levels.
RXCRS
Receive Carrier Sense (Input/Output)
When the AUI port is selected (PORTSEL [1–0] = 00),
an output indicating that the DI input pair is receiving
valid Manchester encoded data from the external
transceiver which meets the signal amplitude and
pulse width requirements. When the 10BASE-T port is
selected (PORTSEL [1–0] = 01), an output indicating
that the RXD input pair is receiving valid Manchester
encoded data from the twisted pair cable which meets
the signal amplitude and pulse width requirements.
RXCRS will be asserted high for the entire duration of
the receive message. When the DAI port is selected
(PORTSEL [1-0] = 10), an input signaling the MACE
device that a receive carrier condition has been
detected on the network, and valid Manchester
encoded data is being presented to the MACE device
on the RXDAT line. When the GPSI port is selected
(PORTSEL [1-0] = 11), an input signalling the internal
MAC core that valid NRZ data is being presented on
the RXDAT input. Operates at TTL levels.
High Impedance
TXEN Output
TXEN Output
TXEN Output
TXEN Output
High Impedance (Note 3)
Pin Function