am79c901a Advanced Micro Devices, am79c901a Datasheet - Page 33

• Manufacturer Part Number: am79c901a
• Description: Homephy Single-chip 1/10 Mbps Home Networking Phy
• Manufacturer: Advanced Micro Devices

D slice threshold
The SYNC interval is followed by six AID symbols
(symbols 1 through 6). Transmit timing is shown in Fig-
ure 17; receive timing in Figure 18. Data is encoded in
the relative position of each pulse with respect to the
previous one. A pulse may occur at one, and only one,
of the four possible positions within an AID symbol
yielding two bits of data coded per AID symbol.
The decoded bits from the AID symbols 1 to 4 produce
eight bits of Access ID which is used to identify individ-
ual HomePNA stations and to detect collisions. The
MSB is encoded in AID Symbol 1 and is the leftmost bit
in Table 7.
pulse 0
SYNC_START
TIC=0
pulse 0
SYNC_START
TIC=0
AID Symbol 0
Detected envelope
AID Symbol 0
END_RCV_BLANK
SYNC_END
TIC=126
SYNC_END
Figure 17. AID Symbol Transmit Timing
TIC=126
Figure 18. AID Symbol Receive Timing
pulse 1
TIC=129
TIC=0
and
pulse 1
P R E L I M I N A R Y
TIC=129
and
TIC=0
AID_Position_0
Receiver
Transmitter
AID Symbol 1
Am79C901A
AID_Position_1
AID_Position_0
TIC=66
AID_Position_2
AID Symbol 1
AID_Position_1
TIC=86
TIC=66
pulse 2
shown in position 1
TIC=106
AID_Position_3
AID_Position_2
TIC=86
Table 7. Access ID Symbol Pulse Positions and
Position
pulse 2
shown in position 1
Pulse
TIC=126
TIC=106
AID_Position_3
1
2
3
4
TIC=126
TIC=129
TIC=0
and
TICs from Beginning of AID
TIC=129
TIC=0
and
AID Symbol 2
Encoding
Symbol
106
126
66
86
AID Symbol 2
AID_GUARD_INTERVAL
Bit Encoding
22304B-19
22304B-20
00
01
10
11
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