AM79C864A Datasheet, PDF (37/51 Pages) Advanced Micro Devices – Physical Layer Controller With Scrambler (PLC-S)

PRELIMINARY
Reset
1
Inserted
PCI3
6
Removed
PCI0
2
7
3
4
Insert
Scrub
PCI1
5
Remove
Scrub
PCI2
15535B-15
AMD
Notes:
1. Class = S or PCM_MAINT
2. Not (SC_ JOIN and not START_SCRUBBING)
3. SET_SC_ JOIN
4. TPC > T_SCRUB and (SC_JOIN and not
START_SCRUBBING)
5. SET_SC_ JOIN
6. Not SET_SC_JOIN and START_SCRUBBING
7. TPC > T_SCRUB
Signals on PCI State Machine:
SC_JOIN:
This signal is output by the PCM state machine and indi-
cates that is has reached the ACTIVE state and scrubbing
may be started.
SET_SC_JOIN:
This signal is output by the PCM state machine and is as-
serted during the clock cycle before SC_JOIN is asserted.
CLASS_S:
This bit in the PLC_CNTRL_B register, when set, indicates
that the station is of type CLASS_S.
START_SCRUBBING:
This signal is asserted by the PCM state machine when the
station has joined the ring (SC_JOIN is asserted) and a
Break condition occurs. It causes the PCI state machine to
enter the REMOVE_SCRUB state.
PCM_MAINT:
This signal indicates that the PCM state machine is in the
MAINT state.
Figure 3. PCI State Machine
Decoder
The Decoder performs the 4B/5B decoding of received
data symbols. The five bits of data from the Elasticity
Buffer are decoded into four bits of data and one control
bit, with the high order bit being the control bit. The de-
coded symbol pairs are then sent to the MAC. Although
the Decoder operates on symbol pairs, each symbol is
decoded independently of the other.
Until the PCM has completed establishing a connection
for the physical link, the PHY_INVALID symbol is output
by the Decoder. Whether the output of the decoder or
the data on TX 9–0 is output on RX 9–0 is dependent on
the CLASS_S bit in the PLC_CNTRL_B register. In ad-
dition, a Violation symbol (V) shall be generated when
an input error condition has been detected, such as an
Elasticity Buffer error (buffer overflow or underflow).
PHY_INVALID takes precedence over Violation, so if an
Elasticity Buffer error occurs while the Current Line
State is Quiet, Halt, Master, or Noise then
PHY_INVALID (1F in hex) is given to MAC.
The symbol decoding is shown in Table 15.
Am79C864A
3-39