STLC3080 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STLC3080' PDF : 23 Pages View PDF
STLC3080
APPENDIX A
The flow-chart in Fig.A1 describes the sequence
of state machine supervising the STLC3080 op-
eration when the control is set for Active mode,
D0 D1 D2= 1 X X.
The state machine is a synchronous sequential
circuit internally clocked by a free running oscilla-
tor ; the ringing frequency applied at the CKRING
input is used to generate the long time delay
WTIME=128xCKRING necessary for proper op-
eration as further described.
External control is supposed to be set for Active
mode :
D0 D1 D2= 1 X X.
OH-HI : line status flag , set High when Off-Hook
condition is detected in High Impedance Feeding;
it differs from OHK because it’s sensitive to the
longitudinal current.
OHK: line status flag , set High when Off-Hook
condition is detected in Stand-By or in Active
mode; it differs from OH-HI for its immunity to lon-
gitudinal current .
DLY: time-out flag, it is set High to resume, with
a given delay, the High Impedance Feeding when
an On-Hook condition (OHK=Low) is detected in
Stand-By or Active state.
1) Note that in this section the word ”mode” has
been used to indicate the operating status set
with D0, D1 and D2 pin: the word ”state” has
been used to indicate an internal status of the
finite state machine.
Flow-chart Description
H) A Reset condition, generated at Power On or
setting RES pin Low, forces a Power-Down
condition.
A) High Impedance Feeding is entered after the
Active mode word is set and its maintained un-
til an Off-Hook condition is detected (OH-
HI=High) ; in this case Stand-By state entered.
B) Stand-By state is set to perform a validity
check of the Off-Hook status of the line before
entering Active state. If it is confirmed
(OH=High), immediately Active state is en-
tered.
If not , Stand-By state remains set for a time
period WTIME generated through a counter
that times out after 128 x CKRING ; DLY=High
signals the state machine the time out to re-
sume the High Impedance Feeding.
An OHK = High detected during WTIME will im-
mediately enter Active state.
C) Active state is set for conversation and
DET=Low signals to the controller the Off-Hook
condition of the line.
The status remains set as long as OHK=High
(Off-Hook).
D) When OHK=Low is detected (On Hook), DET
is immediately set High whereas Active state is
maintained for the period WTIME; when it ex-
pires DLY is set High and High Impedance
Feeding is resumed.
If, during WTIME, OHK=High is detected Off
Hook), the state is returned to C) , i.e. Active
with DET=Low.
E) Ringing mode is set when D0 = D1 = 0 and D2 = 1.
After ring trip detection the SLIC is automat-
ically set in Active state (reverse or normal po-
larity according to D2 value set before ringing
mode). Ring trip detection is indicated by DET
pin: when it happens the SW must remove the
ringing mode word (001) and set the Active
mode word (100).
F) On-Hook Tx mode is selected when D0 = 0,
D1 = 1 and D2 = X.
After Off Hook detection the SLIC is automat-
ically set in Active state.
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