SI2493-C-FT Silicon Laboratories Inc, SI2493-C-FT Datasheet - Page 125

• 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

To set the Si2457 to monitor loop current in the off-hook
state, the host issues the following commands:
3.5.10. Overcurrent Detection Example
The Si2493/57/34/15/04 has a built-in overcurrent
detection feature (disabled by default) that measures
loop current a programmable amount of time after going
off-hook. This allows the modem to detect an improper
line condition. The overcurrent detect feature is enabled
by setting U70[11] (OCDM) = 1
the modem goes off-hook, loop current is measured and
set by U77[8:0] (OHT). The default delay is 16 ms. After
the delay, current is sampled every 1 ms. An
overcurrent is detected if two consecutive samples
indicate an overcurrent condition. If this feature is
enabled and excessive current is detected, the Si2493/
57/34/15/04 sends the “X” result code and triggers an
interrupt by asserting the INT pin or by setting the INT
bit in the parallel mode. After an interrupt is received,
the host issues the AT:I command to verify the OCD
interrupt and clear the OCD bit. The delay between
modem off-hook and loop current measurement is set
by the OHT bits. OHT is a 9-bit register with 1 ms units.
The default delay is 16 ms. When the modem is off-
hook in an overload condition, LVCS = 11111 (full
scale—overload error condition), an X is sent to the
DTE, and the OCD bit is set.
The Overcurrent Detection feature is controlled by
changing U-Register settings. The registers and bits
that control these features are shown in Table 84.
AT:R79<CR>
Command
Command
AT:R79
ATH1
Function
Function
Host reads the loop voltage
from the LVCS Register U79
bits 4:0 while the modem is
on-hook.
To go off-hook
Host reads loop current from
the LVCS Register U79 bits
4:0 while the modem is off-
hook.
b
. During the time after
Rev. 0.9
3.5.11. Pulse/Tone Dial Decision
There are three methods to detect whether a telephone
line supports DTMF dialing or pulse dialing only. The
first method, which is the simplest, may require the
modem to go off-hook more than once. The second
method is slightly more complicated but does not
require the modem to go off-hook multiple times.
Method #1: Multiple Off-Hook Transitions:
Use DTMF to dial the desired number with the ATDT
command. If the line accepts tone dialing, the call is
completed, and connection to the remote modem
proceeds as usual.
If the line only allows pulse dialing, the modem hangs
up and reports UN-OBTAINABLE NUMBER. This
indicates that the modem detected a dial tone after the
DTMF dial attempt. Dial the number again using the
ATDP command instead of ATDT to use pulse dialing.
Method #2: Single Off-Hook Transition:
Use this method if it is undesirable for the modem to go
off-hook more than once or to DTMF dial a single digit.
This method is somewhat more complicated and is best
illustrated with an example, dialing the number 1234
below. This method only works with Rev. F and later.
Set bit 7 of U-register 7A (U7A[7](DOP) = 1b) and send
ATDT1;<cr> (Dial the first digit using DTMF and wait for
a response). A response of “OK” indicates the DTMF
digit, 1, was sent, and you can continue. If a response of
“NO DIALTONE” is received, the command failed
because there was no dial tone (no line available), and
the call cannot be completed.
If a response of “OK” is received after sending
ATDT1;<cr>, continue by sending ATDTW;<cr> to
perform the second dial tone detection and wait for a
response. A response of “NO DIALTONE” “OK”
indicates that no dial tone was detected for two
seconds, and the line is DTMF capable. Complete the
dialing
beginning with the second number since the first
number was successfully sent initially).
Register
U67
U70
U70
U77
U79
by
Table 84. Overcurrent Detection
8:0
4:0
Bit
11
sending
7
3
OCDM
Value
LVCS
DCR
OCD
OHT
ATDT2345<cr>
Overcurrent Detect
Overcurrent Detect
Function
DC Impedance Select
Mask
Off-Hook Time
Line Voltage Current
Sense
(DTMF
AN93
dial
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