am79c940 Advanced Micro Devices, am79c940 Datasheet - Page 19

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

PIN DESCRIPTION
Network Interfaces
The MACE device has five potential network interfaces.
Only one of the interfaces that provides physical net-
work attachment can be used (active) at any time. Se-
lection between the AUI, 10BASE-T, DAI or GPSI ports
is provided by programming the PHY Configuration
Control register. The EADI port is effectively active at all
times. Some signals, primarily used for status reporting,
are active for more than one single interface (the CLSN
pin for instance). Under each of the descriptions for the
network interfaces, the primary signals which are
unique to that interface are described. Where signals
are active for multiple interfaces, they are described
once under the interface most appropriate.
Attachment Unit Interface (AUI)
CI+/CI
Control In (Input)
A differential input pair, signalling the MACE device that
a collision has been detected on the network media, in-
dicated by the CI inputs being exercised with 10 MHz
pattern of sufficient amplitude and duration. Operates at
pseudo-ECL levels.
DI+/DI
Data In (Input)
A differential input pair to the MACE device for receiving
Manchester encoded data from the network. Operates
at pseudo-ECL levels.
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
TXDAT+ Configuration
TXDAT– 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
DO+/DO
Data Out (Output)
A differential output pair from the MACE device for
transmitting Manchester encoded data to the network.
Operates at pseudo-ECL levels.
Digital Attachment Interface (DAI)
TXDAT+/TXDAT–
Transmit Data (Output)
When the DAI port is selected, TXDAT are configured
as a complementary pair for Manchester encoded data
output from the MACE device, used to transmit data to a
local external network transceiver. During valid trans-
mission (indicated by TXEN low), a logical 1 is indicated
by the TXDAT+ pin being in the high state and TXDAT–
in the low state; and a logical 0 is indicated by the
TXDAT+ pin being in the low state and TXDAT– in the
high state. During idle (TXEN high), TXDAT+ will be in
the high state, and TXDAT– in the low state. When the
GPSI port is selected, TXDAT+ will provide NRZ data
output from the MAC core, and TXDAT– will be held in
the LOW state. Operates at TTL levels. The operations
of TXDAT+ and TXDAT– are defined in the following
tables:
High Impedance
High Impedance (Note 2)
High Impedance (Note 2)
TXDAT+ Output
TXDAT+ Output
High Impedance (Note 2)
High Impedance
High Impedance
High Impedance
TXDAT– Output
LOW
High Impedance
Pin Function
Pin Function
AMD
19