SI3015-FS Silicon Laboratories Inc, SI3015-FS Datasheet - Page 19

• Manufacturer Part Number: SI3015-FS
• Description: SI2400 ISOMODEM LINE-SIDE
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3015-FS

• Data Format: V.90
• Interface: Serial
• Voltage - Supply: 3.3 V ~ 5 V
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Baud Rates: -

Reporting of an On-Hook Intrusion
The reporting of an on-hook intrusion is the same
whether or not the differential or absolute algorithm is
chosen.
An “i” result code is sent when an intrusion is detected.
Conversely an “I” result code is sent when an intrusion
has terminated. S14[1] (IND) indicates the current
intrusion status and is set for as long as an intrusion is
detected.
In addition, if the LVCS returns a value of zero, an “l”
result code is sent to the host. If the LVCS becomes
non-zero after having gone to zero, an “L” result code is
sent to the host. S14[2] (NLD) indicates the current line
voltage status and is set for as long as the LVCS is zero.
It is possible to suppress the result codes by setting
S14[7] MRCD = 1b and selectively re-enabling desired
result codes using the S62 register. Suppressing result
codes in this fashion does not affect the setting of the
NLD and IND bits of the S14 register. Suppressing the
result codes is the best approach if polling the S14
register to monitor the intrusion status is preferred.
It is also possible to suppress the result codes by
setting S33[6] (DON). However, this approach will stop
the updating of the S14 register, rendering the on-hook
intrusion algorithm completely disabled. This approach
may be used if the host checks LVCS directly prior to
going off-hook.
Off-Hook Intrusion Detection
When the Si2400 is off-hook, it can detect another
phone going off-hook by monitoring the dc loop current.
The loop current sense transfer function is shown in
Figure 8 with the upper curve representing CTR21
LVCS
BITS
30
25
20
15
10
5
0
0 3 6 9 12 15 18 21 24
Figure 8. Loop Current—LVCS Transfer Function
CTR21
27
30 33 36 39 42 45 48 51 54 57 60 63 66 69 72
Rev. 1.1
Loop Current
(current limiting) operation and the lower curve
representing all other modes. The overload points
indicate excessive current draw. The user can read
these bits directly through SDB (LVCS). Note that as in
the line voltage sense, there is hysteresis between
codes (0.375 mA for CTR21 mode and 0.75 mA for the
alternate mode).
The off-hook intrusion algorithm does not begin to
operate immediately after going off-hook. This is to
avoid triggering an off-hook intrusion interrupt due to off-
hook transients. The time between going off-hook and
enabling the intrusion algorithm defaults to 1 second
and may be set via S82[7:4] (IST).
Once the intrusion settling time (IST) has elapsed, the
Si2400 executes one of the three off-hook intrusion
algorithms,
SDF[6:0] (DSGR) and S13[4] (OFHD). See Table 15.
Differential Algorithm #1 (default)
If (LVCS (t – 800 ms) – LVCS (t)) > S12[7:5] (DCL), then
an intrusion is deemed to have taken place. If (LVCS (t)
– LVCS (t – 800 ms)) > DCL, then the intrusion is
deemed to have completed. Default DCL is 2. This
comparison occurs every 200 ms.
(mA)
Table 15. Off-Hook Intrusion Algorithms
Differential #1
Differential #2
Algorithm
Absolute
75 78 81 84 87 90 93
depending
Overload
on
OFHD
140
the
1
1
0
Si2400
settings
SDF
≠0
0
x
19
of