SI2414 SILABS [Silicon Laboratories], SI2414 Datasheet - Page 37

• Manufacturer Part Number: SI2414
• Manufacturer: SILABS [Silicon Laboratories]

reset), the ISOmodem ignores the register and does not
begin operating the algorithm until two LVCS samples
have been received. Additionally, immediately after a
modem call, the ISOmodem is updated automatically
ACL with the last valid LVCS value before a PPD
intrusion or going back on-hook.
The off-hook intrusion algorithm does not begin to
operate immediately after going off-hook. This is to
avoid triggering a PPD interrupt due to transients
resulting from the ISOmodem itself going from on-hook
to off-hook. The time from when the ISOmodem goes
off-hook to when the intrusion algorithm begins defaults
to 1 second and may be adjusted via the IST register
(U77, bits 15:12). If ACL is written to a non-zero value
before going off-hook, a parallel phone intrusion that
occurs during this IST interval and sustains through the
end of the interval triggers a PPD interrupt.
LVC S
BITS
30
25
20
15
10
5
0
0 3 6
9 12 15 18 21 24 28 30 33 36 39 42 45 47 51 54 57 60 63 66 69 72
Figure 7. Loop Voltage
Rev. 0.9
Loop Voltage (V)
The off-hook intrusion algorithm may, additionally, be
disabled for a period of time after dialing begins via the
IB register (U78, bits 15:14). This avoids triggering a
PPD interrupt due to pulse dialing, open-switch
intervals, or line transients from central office switching.
Intrusion may be disabled from the start of dialing to the
end of dialing (IB = 1), from the start of dialing to the
timeout of the IS (U78, bits 7:0) register (IB = 2), or from
the start of dialing to the connect result code
(CONNECT XXX, NO DIALTONE, or NO CARRIER)
(IB = 3). The off-hook intrusion algorithm is only
suspended (not disabled) during this IB interval.
Therefore, any intrusion that occurs during the IB
interval and sustains through the end of the interval
triggers a PPD interrupt.
Si2456/Si2433/Si2414
75 78 81 84 87
100
37