AN93
Rev. 1.4
175
if LVCS(t) = LVCS (t - 40 ms x OHSR)
and ACL - LVCS(t) < DCL
then ACL = LVCS(t)
if (ACL - LVCS x (t - 40 ms x OHSR) > DCL
and ACL - LVCS x t > DCL
then PPD = 1 and the INT pin (or the INT bit in parallel or SPI mode) is asserted (PPDM = 1)
Using either algorithm, when an intrusion is detected, U70[2] (PPD), Parallel Phone Detect is set. If U70 [10]
(PPDM) (Parallel Phone Detect Mask) is set to 1, an interrupt is triggered. In UART mode the INT pin is asserted;
in parallel or SPI mode the INT bit (Hardware Interface Register 1, [3]) is triggered and, if INTM = 1, (Hardware
Interface Register 1, [4]), INT is asserted. The host can monitor PPD or issue an AT:I command to verify the cause
of an interrupt and clear PPD. The ISOmodem can also be programmed to go on-hook automatically on a PPD
interrupt by setting U77 (HOI) [11] (Hang-Up On Intrusion) to 1. 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 116 lists the U registers and bits used for both Intrusion Detection algorithms.
Table 116. Intrusion Detection
Register Bit(s)
Name
Function
U63
15:8
LCS
Line Current Sense
U6C
15:8
LVS
Line Voltage Sense
U70
10
PPDM
Parallel Phone Detect Mask
U70
2
PPD
Parallel Phone Detect
U76
15:9
OHSR
Off-Hook Sample Rate
U76
8
FACL
Force ACL
U76
7:5
DCL
Differential Current Level – Legacy Algorithm
U76
4:0
ACL
Absolute Current Level – Legacy Algorithm
U77
15:12
IST
Intrusion Settling Time
U77
11
HOI
Hang-Up On Intrusion
U78
15:14
IB
Intrusion Blocking
U78
7:0
IS
Intrusion Suspend
U79
4:0
LVCS
Line Voltage/Current Sense
U83
15:0
NOLN
No Line Threshold %V1
U84
15:0
LIUS
Line-in-use Threshold %V1
U85
15:0
NLIU
Line-in-use/No Line Threshold %V2
UAE
15:8
ACLN
Absolute Current Level – New Algorithm
UAE
7
UAEM
UAE Mode
UAE
6:0
DCLN
Differential Current Level – New Algorithm
Summary of Contents for Si2404
Page 2: ...AN93 2 Rev 1 4 ...
Page 200: ...AN93 200 Rev 1 4 Figure 31 TAM Handset and Speakerphone Voice Paths ...
Page 201: ...AN93 Rev 1 4 201 Figure 32 Si3000 Codec Gain and Signal Selection Options ...
Page 290: ...AN93 290 Rev 1 4 Figure 57 256 Band Spectral Display Figure 58 2048 Band Spectral Display ...
Page 305: ...AN93 Rev 1 4 305 Figure 76 Parallel or SPI Port Interrupt Service Flowchart ...