SI3015-FS Silicon Laboratories Inc, SI3015-FS Datasheet - Page 21

• 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: -

result codes are suppressed, and the ALERT pin is the
only method of reporting an intrusion to the host.
The “i” and “I” result codes may be sent to the host
under the following conditions:
1. If the modem is in the process of establishing a connection
2. If the modem is in command mode and a call is initiated
3. If the modem is used in the security modes (ATDT#!0-!7)
4. If the modem is used in the !2 security mode while the
Once the ALERT pin is asserted as a consequence of
an intrusion, it is the responsibility of the host software
to negate it by clearing SE3[3] (GPD4) directly.
S14[1] (IND) is an indication of the current intrusion
status. It is updated whenever the “i” and “I” result
codes are sent to the host or when the ALERT pin is
asserted. If set, IND indicates that an intrusion event is
in progress. In addition, the status of IND persists for
800 msec after an off hook to on-hook event. After
800 msec has elapsed, IND functions as documented
for the on-hook intrusion algorithm. This delay
preserves the S14 register contents at the time the
ALERT is asserted.
When using the modem as a standard data modem and
the ALERT pin asserts, the host software may need to
force the modem back into command mode. In the
command mode, the host can determine if the ALERT
assertion was caused by an intrusion or a carrier loss by
querying the S14 register.
If the modem is dialing (after the ATDT string but before
the “c”, “v”, or “d” result codes), sending any character
places the modem back into command mode. In the
case in which the modem has already connected (in
data mode after the “c”, “v” or “d” result code has been
sent), an escape sequence is required to place the
modem in the command mode.
The best method of regaining control, without having to
know the exact status of the modem, is by issuing an
escape sequence (asserting the ESC pin and waiting a
short period of time) and sending a carriage return
character. The escape sequence takes care of the case
in which the modem is in the connected state, and the
carriage return character aborts the dialing if the modem
is in the process of dialing to get a connection. If the
modem is already on-hook and in command mode, the
carriage return character and escape sequence are
benign events.
using the “ATDT#<cr>” or “ATA<cr>” commands and prior
to the “c”, “v”, or “d” result codes.
using “ATDT#;” command.
(except !2).
modem is not actively receiving/sending FSK data.
Rev. 1.1
Loop Current Detection
In addition to monitoring parallel phone intrusion, it is
possible to monitor the loss of loop current. This feature
can be enabled by setting SE82[3] (LCLD) = 1. This
feature is disabled by default. If the loop current is too
low for normal DAA operation, the “l” result code is sent,
and S14[2] (NLD) is set. Once the loop current returns
to a normal current state, the “L” result code is sent and
S14[2] (NLD) is cleared. The ALERT pin is also
asserted if enabled. The “L” and “l” result codes are not
always sent. The principles governing the reporting of
the “i” and “I” result codes apply to the “L” and “l” result
codes. The status of the S14 register is unchanged for
800 msec after an off-hook to on-hook event. This delay
preserves the S14 register contents at the time the
ALERT is asserted.
Carrier Detect/Loss
The Si2400 can provide the functionality of a loss-of-
carrier pin similar to the CD pin functionality in an RS-
232 connection. If programmed as an ALERT, GPIO4
will go high in data mode when either parallel phone
intrusion or a loss-of-carrier is detected. When used in
this manner, the host detects a low-to-high transition on
GPIO4 (ALERT), escapes into command mode, and
reads S14[1] (IND). If high, IND indicates intrusion. If
low, IND indicates loss-of-carrier.
A carrier detect function may also be implemented by
setting SE2[3:2] (GPIO2) = 01b, SE4[0] (TRSP) =0b,
and SOC[7] (CDE) = 1b.
Overcurrent Protection
The Si2400 has built in protection to avoid damage to
the device due to overcurrent situations. An example
situation occurs when plugging the modem into a digital
PBX outlet and attempting to go off-hook. Digital PBX
systems vary, but many can provide a dc feed voltage of
up to 70 V and therefore have the ability to deliver
hundreds of milliamps of current into the DAA.
The Si2400 will always go off hook with the current-
limiting mode enabled. This allows no possibility of
damage for voltages up to about 48 V. However, at
higher voltages the 43 V Zener protection device will
begin to conduct and could be damaged if the power is
applied for too long.
The Si2400 will detect the value of the loop current at a
programmable time set by S32 (OCDT) after going off-
hook (default = 20 ms). If the loop current is too high, an
“x” will be echoed back to the host to indicate a fault
condition. The host may then check S14[3] (OD) to
confirm an overcurrent condition. Placing the modem
on-hook immediately to avoid possible damage due to a
Si2400
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