am79c864a Advanced Micro Devices, am79c864a Datasheet - Page 35

• Manufacturer Part Number: am79c864a
• Description: Physical Layer Controller With Scrambler Plc-s
• Manufacturer: Advanced Micro Devices

PCI Operation
The PCI State Machine works in conjunction with the
PCM state machine to control the data paths of the
PLC-S on the MAC side (the RX 9–0 and TX 9–0 paths).
There are three primary functions of the PCI state
machine:
The operation of the PCI state machine depends on
whether the CLASS_S bit in the PLC_CNTRL_B regis-
ter is set and whether the PCM state machine is in the
MAINT state.
PCI Operation for Non-Class S Type Station
After a reset the PCI state machine will be in the RE-
MOVED state. If the station is not of type Class S, then
the PLC-S will be in the bypass mode where the data in-
put on TX 9–0 is directly output on RX 9–0.
State
PC0(OFF)
PC1(BREAK)
PC2(TRACE)
PC3(CONNECT)
PC4(NEXT)
PC5(SIGNAL)
PC6(JOIN)
PC7(VERIFY)
PC8(ACTIVE)
PC9(MAINT)
Provide a bypass path between TX 9–0 and
RX 9–0
Provide a scrubbing function upon the insertion
and removal of a station from the ring
Provide a direct path between the PDT/PDR and
the MAC
Description
The PCM enters the OFF state whenever the RST pin is asserted or whenever the
PCM_CNTRL field of the PLC_CNTRL_B register is set to 11 (PC_Stop). The PCM stays in
this state until PC_Start is issued or the PC_MAINT bit is set.
This is the entry point in the start of a PCM connection. The PCM enters this state when
PC_Start is issued, or while it is in the process of forming a connection when any of various
error conditions occur (such as receipt of Quiet Line State, a timeout, etc.).
The TRACE state is issued to localize a stuck Beacon condition. It is entered when PC_Trace is
issued while the PCM is in the ACTIVE state.
This state is used to synchronize the ends of the connection for the signaling sequence. It is
entered from the BREAK state.
This state is used to separate the signaling performed in the SIGNAL state and to perform the
Link Confidence Test. It is entered from the CONNECT state or SIGNAL state.
In this state individual bits of information are communicated across the connection by
transmitting either Halt symbols or alternating Halt and Quiet symbols (Master Line State).
The PCM transmits and receives bits of information at the same time. This state is entered from
the NEXT state.
This state is the first of three states that leads to an active connection. It is entered from the
NEXT state.
This state is the second state in the path to the ACTIVE state. It will not be reached by a
connection that is not synchronized.
The ACTIVE state is the state where the PHY has been incorporated into the ring. It is entered
from the VERIFY state.
This state is used to override the normal PCM operation for test purposes or so that the PCM
operation may be done completely in software. In this state the data path configuration and the
transmit data stream are controlled by the Node Processor.
Table 13. PCM State Description
P R E L I M I N A R Y
Am79C864A
When the PCM state machine enters the ACTIVE state
and asserts the SC_JOIN Flag, the PCI state machine
enters the INSERT_SCRUB state and Idle symbol pairs
are sourced on RX 9–0. At the same time, the PCM state
machine causes Idle symbols to be output on
TDAT 4–0.
The PCI state machine remains in the INSERT_SCRUB
state for T_SCRUB length of time, after which it enters
the INSERTED state. Upon entering the INSERTED
state, the PCM_ENABLED interrupt is asserted. In this
state, a direct path exists from TX 9–0 to TDAT 4–0.
If for some reason the connection is broken and the PCI
state machine enters the REMOVE_SCRUB state, Idle
symbol pairs are sourced on RX 9–0. Because the PCM
state machine is in the BREAK state, Quiet symbols are
sourced on TDAT 4–0. While scrubbing is being per-
formed, the PCM state machine will not re–start the con-
nection process. The PCI state machine remains in the
REMOVE_SCRUB state for T_SCRUB length of time
and then enters the REMOVED state.
Note that if the connection is broken while the PCI state
machine is in the INSERT_SCRUB state, scrubbing will
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