Silicon Laboratories SI2494/39 manual Intrusion Detection, Register Bits Name Function, ATH1

AN93

Table 102. Intrusion Detection

Register	Bit(s)	Name	Function
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
U76	4:0	ACL	Absolute Current Level
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

The ISOmodem has an internal analog-to-digital converter used to monitor the loop voltage when on-hook and loop current when off-hook to check for parallel devices going off-hook. The host measures loop voltage or current by reading U79 [4:0] (LVCS). To set the ISOmodem to monitor loop voltage in the on-hook state, the host issues the following commands:

Command	Function
AT:R79	Host reads the loop voltage
	from the LVCS Register U79
	bits 4:0 while the modem is
	on-hook.

To set the ISOmodem to monitor loop current, the host issues the following commands:

Command	Function
ATH1	To go off-hook
AT:R79	Host reads loop current from
	the LVCS Register U79 bits
	4:0 while the modem is off-
	hook.

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