am79c940 Advanced Micro Devices, am79c940 Datasheet - Page 21

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

DXCVR
Disable Transceiver (Output)
An output from the MACE device to indicate the network
port in use, as programmed by the ASEL bit or the
PORTSEL [1–0] bits. The output is provided to allow
power down of an external DC-to-DC converter, typi-
cally used to provide the voltage requirements for an ex-
ternal 10BASE2 transceiver.
When the Auto Select (ASEL) feature is enabled, the
state of the PORTSEL [1–0] bits is overridden, and the
network interface will be selected by the MACE device,
dependent only on the status of the 10BASE-T link. If the
Note: RWAKE and ASEL are located in the PHY Configuration Control register (REG ADDR 15). PORTSEL [1–0] and
ENPLSIO are located in the PLS Configuration Control register (REG ADDR 14). All bits must be programmed prior to the
assertion of the SLEEP pin.
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
Pin
0
0
0
0
0
0
0
0
0
0
SLEEP
0
1
1
1
1
1
RWAKE AWAKE
Bit
0
1
1
1
1
1
1
1
1
0
PORTSEL
[1–0]
XX
XX
Bit
00
01
10
11
0
0
0
0
0
0
0
1
1
1
ASEL
Bit
X
X
0
0
0
0
1
1
1
1
DXCVR Configuration—SLEEP Operation
ENPLSIO
X
1
1
1
1
0
Impedance
Impedance
Impedance
Impedance
Impedance
Impedance
Impedance
LNKST
HIGH
LOW
High
High
High
High
High
High
High
RXCRS Configuration
Pin
X
Am79C940
Interface Description
Sleep Mode
AUI
10BASE-T
DAI Port
GPSI
Status Disabled
PORTSEL
[1–0] Bits
link is active (LNKST pin driven LOW) the 10BASE-T
port will be used as the active network interface. If the
link is inactive (LNKST pin pulled HIGH) the AUI port will
be used as the active network interface. Auto Select will
continue to operate even when the SLEEP pin is as-
serted if the RWAKE bit has been set. The AWAKE bit
does not allow the Auto Select function, and only the re-
ceive section of 10BASE-T port will be active (DXCVR =
HIGH).
Active (HIGH) when either the 10BASE-T or DAI port is
selected. Inactive (LOW) when the AUI or GPSI port is
selected.
XX
0X
0X
0X
0X
0X
00
01
10
11
10BASE-T with EADI port
10BASE-T with EADI port
10BASE-T with EADI port
AUI with EADI port
AUI with EADI port
AUI with EADI port
Description
Interface
10BASE-T
Invalid
Invalid
Sleep
Mode
High Impedance
RXCRS Output
RXCRS Output
RXCRS Input
RXCRS Input
High Impedance (Note 2)
Pin Function
Impedance
Function
AMD
HIGH
HIGH
HIGH
HIGH
HIGH
High
LOW
LOW
LOW
LOW
Pin
21