AM79C978 Advanced Micro Devices, AM79C978 Datasheet - Page 98

• Manufacturer Part Number: AM79C978
• Description: Single-Chip 1/10 Mbps PCI Home Networking Controller
• Manufacturer: Advanced Micro Devices

10BASE-T Physical Layer
The 10BASE-T block consists of the following sub-
blocks:
Refer to Figure 50 for the 10BASE-T block diagram.
Twisted Pair Transmit Function
Data transmission over the 10BASE-T medium re-
quires use of the integrated 10BASE-T MAU and uses
the differential driver circuitry on the TX± pins.
TX± is a differential twisted-pair driver. When properly
terminated, TX± will meet the transmitter electrical re-
quirements for 10BASE-T transmitters as specified in
98
Table 28. Legal I/O Accesses in Double Word I/O
Table 27. I/O Map in DWord I/O Mode (DWIO = 1)
AD[4:0]
0XX00
0XX00
10000
10100
10000
10100
11000
11000
00h - 0Fh
— Transmit Process
— Receive Process
— Interface Status
— Collision Detect Function
— Jabber Function
— Reverse Polarity Detect
Offset
1Ch
10h
14h
18h
BE[3:0]
0000
0000
0000
0000
0000
0000
0000
0000
No. of Bytes
Mode (DWIO =1)
16
4
4
4
4
Type
WR
WR
WR
WR
RD
RD
RD
RD
RAP (shared by RDP and
DWord read of APROM
locations 3h (MSB) to 0h
(LSB),
7h to 4h, Bh to 8h, or Fh to
Ch
DWord read of RDP
DWord read of RAP
DWord read of Reset
Register
DWord write to APROM
locations 3h (MSB) to 0h
(LSB),
7h to 4h, Bh to 8h, or Fh to
Ch
DWord write to RDP
DWord write to RAP
DWord write to Reset
Register
Reset Register
Register
APROM
Comment
BDP)
RDP
BDP
Am79C978
IEEE 802.3, Section 14.3.1.2. The load is a twisted pair
cable that meets IEEE 802.3, Section 14.4.
The TX± signal is filtered on the chip to reduce har-
monic content per Section 14.3.2.1 (10BASE-T). Since
filtering is performed in silicon, TX± can be connected
directly to a standard transformer. External filtering
modules are not needed.
Twisted Pair Receive Function
The RX+ port is a differential twisted-pair receiver.
When properly terminated, the RX+ port will meet the
electrical requirements for 10BASE-T receivers as
specified in IEEE 802.3, Section 14.3.1.3. The receiver
has internal filtering and does not require external filter
modules or common mode chokes.
Signals appearing at the RX± differential input pair are
routed to the internal decoder. The receiver function
meets the propagation delays and jitter requirements
specified by the 10BASE-T standard. The receiver
squelch level drops to half its threshold value after un-
squelch to allow reception of minimum amplitude sig-
nals and to mitigate carrier fade in the event of worst
case signal attenuation and crosstalk noise conditions.
Twisted Pair Interface Status
The Am79C978 device will power up in the Link Fail
state. The Auto-Negotiation algorithm will apply to
allow it to enter the Link Pass state.
Figure 50. 10BASE-T Transmit and Receive Data
Clock
Manchester
Encoder
TX Driver
TX±
Data
Paths
Clock
Manchester
RX Driver
Decoder
Squelch
Circuit
RX±
Data
22206B-54