SI2493-C-FT Silicon Laboratories Inc, SI2493-C-FT Datasheet - Page 124

• Manufacturer Part Number: SI2493-C-FT
• Description: 56 KBPS, V.92 ISOMODEM SYSTEM-SIDE - LEAD-FREE TSSOP 0 TO 7
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2493-C-FT

• Mfg Application Notes: SI2493/57/34/15/04, Appl Note AN93
• Data Format: V.21, V.22, V.23, V.29, V.32, V.34, V.90, V.92, Bell 103, Bell 212A
• Baud Rates: 56k
• Interface: Parallel
• Voltage - Supply: 3 V ~ 3.6 V
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AN93
To prevent polarity reversals from being detected as a
loss of loop current, a debounce timer controlled by U-
registers 50 and 51 is used. However, if the HOI bit is
set, a parallel phone intrusion while off-hook will give a
“LINE IN USE” result code to indicate that the Si2493/
57/34/15/04 has gone on-hook due to a parallel phone
intrusion.
3.5.9. Intrusion Detection—Off-Hook Condition
When the ISOmodem is off-hook, the U79[4:0] (LVCS)
value
ISOmodem is typically in the data mode, and it is
difficult for the host to monitor the LVCS value. For this
reason, a controller-based off-hook intrusion algorithm
is used.
There is a delay between the ISOmodem going off-hook
and the start of the intrusion algorithm set by
U77[15:12] (IST) (Intrusion Settling Time). This avoids
false intrusion detection due to loop transients during
the on-hook to off-hook transition. The off-hook intrusion
algorithm monitors the value of LVCS at a sample rate
determined
compares each LVCS sample to the reference value in
U76[4:0] (ACL). ACL = 0 at the first off-hook event after
reset unless a value is written to it by the host. If
ACL = 0, the ISOmodem does not begin the intrusion
algorithm until after two LVCS samples have been
received. If the host writes a non-zero value to ACL
prior to the ISOmodem going off-hook, a parallel phone
intrusion occurring during the IST interval and
maintained until the end of the IST interval triggers a
PPD interrupt. The ISOmodem also automatically
updates ACL with the LVCS value while off-hook if an
intrusion has not occurred. An ACL value can be written
by the host and forced to remain unchanged by setting
U76[8] (FACL) = 1b. If LVCS is lower than ACL by an
amount greater than the value set in U76[7:5] (DCL)
(6 mA
U70[2] (PPD),
U70[10] (PPDM) (Parallel Phone Detect Mask) is set to
1b (default condition), the INT pin (Si2493/57/34/15/04,
pin 14) in serial mode or the INT bit (Parallel Interface
Register 1, bit 3) in parallel mode is also triggered. The
host can monitor PPD or issue an AT:I to verify the
cause of an interrupt and clear PPD. The host can take
the appropriate action when the intrusion is confirmed.
The Intrusion Detection Algorithm is as follows:
if LVCS(t) = LVCS (t – 40 ms x OHSR)
and ACL – LVCS(t) < DCL
then ACL = LVCS(t)
if (ACL – LVCS (t – 40 ms x OHSR) > DCL
and ACL – LVCS(t) > DCL
124
represents
default)
by
Parallel
U76[15:9] (OHSR).
for
loop
two
Phone
current.
consecutive
Detect
Additionally,
The
is
algorithm
samples,
set.
the
Rev. 0.9
If
then PPD = 1
and INT (or INT bit in parallel mode) is asserted
(PPDM = 1)
The ISOmodem can also be programmed to go on-hook
automatically
U77 (HOI)[11] (Hang-Up On Intrusion) to 1b.
The off-hook intrusion algorithm may be suspended for
a period defined by U78[15:14] (IB) after the start of
dialing. This guards against false PPD detects due to
dial pulses or other transients caused by Central Office
switching.
Table 83 lists the U-Registers and bits used for Intrusion
Detection.
The Si2493/57/34/15/04 has an internal analog-to-
digital converter used to monitor the loop voltage when
on-hook and loop current when off-hook to check for
parallel devices going off-hook. The host measures loop
voltage or current by reading U79[4:0] (LVCS). To set
the Si2493/57/34/15/04 to monitor loop voltage in the
on-hook state, the host issues the following commands:
Register Bit(s)
U70
U70
U76
U76
U76
U76
U77
U77
U78
U78
U79
U83
U84
U85
Table 83. Intrusion Detection
15:12
15:14
15:9
15:0
15:0
15:0
7:5
4:0
7:0
4:0
10
11
2
8
on
PPDM
OHSR
a
NOLN
Name
LVCS
FACL
NLIU
LIUS
PPD
DCL
ACL
HOI
IST
IB
IS
PPD
Parallel Phone Detect
Off-Hook Sample Rate
Force ACL
Differential Current
Intrusion Settling Time
Intrusion Suspend
No Line Threshold %V1
Line-in-use Threshold
Function
Mask
Parallel Phone Detect
Level
Absolute Current Level
Hang-Up On Intrusion
Intrusion Blocking
Line Voltage/Current
Sense
%V1
Line-in-use/No Line
Threshold %V2
interrupt
by
setting