AM79C978 Datasheet, PDF (189/261 Pages) Advanced Micro Devices – Single-Chip 1/10 Mbps PCI Home Networking Controller

TBR0: 10BASE-T PHY Control Register (Register 0)
Table 65. TBR0: 10BASE-T PHY Control Register (Register 0)
Reg Bits
Name
Description
Read/Write
(Note 1)
When write: 1 = PHY software reset,
0 = normal operation.
0
15 Soft Reset (Note 2)
When read: 1 = reset in process,
0 = reset done.
R/W, SC
0
14
Loopback
0 = asserts Loopback mode,
1 = deasserts Loopback mode
R/W
0
13
Speed Selection 1 = 100 Mbps,
(Note 3)
0 = 10 Mbps
R/W
0
12
Auto-Negotiation 1 = enable Auto-Negotiation,
Enable
0 = disable Auto-Negotiation
R/W
0
11
Power Down
1 = power down,
0 = normal operation
R/W
0
10
Isolate
(Note 4)
1 = electrically isolate PHY
0 = normal operation
R/W
0
9
Restart Auto-
Negotiation
1 = restart Auto-Negotiation,
0 = normal operation
R/W, SC
0
8
Duplex Mode
(Note 3)
1 = Full-Duplex,
0 = Half-Duplex
R/W
0
7
Collision Test
1 = enable COL signal test,
0 = disable COL signal test
R/W
0
6-0
Reserved
Write as 0, ignore on read
RO
Notes:
1. R/W = Read/Write, SC = Self Clearing, RO = Read only.
2. Soft Reset does not reset the PDX block. Refer to the Soft Reset Section for details.
3. Bits 8 and 13 have no effect if Auto-Negotiation is enabled (Bit 12 = 1).
4. If the ISOL pin of the chip and the Isolate bit in Register 0 is 1, this bit will be set.
Default
Value
Soft
Reset
0
0
0
0
1
1
1
1
0
0
1
1
0
0
Retains
1
previous
value
0
0
0
0
Am79C978
189