Silicon Laboratories SI2494/39, SI2493/57/34/15/04 manual U76 Bit Map, U77 Bit Map

AN93

			Table 74. U76 Bit Map
Bit	Name	Function
15:9	OHSR	Off-Hook Sample Rate for Intrusion Detection (40 ms units).
		(1 second default)
8	FACL	Force ACL.
		0	= While off-hook, ACL is automatically updated with LVCS value.
		1	= While off-hook, ACL saves previously written value.
7:5	DCL	Differential Current Level (3 mA units, 6 mA default)
4:0	ACL	Absolute Current Level (3 mA units, 0 mA default)

U77 is a bit-mapped register that controls parameters relating to intrusion detection and overcurrent detection. U77 resets to 0x401E with a power-on or manual reset (see Table 75).

Bits 15:12 (IST) set the delay between the time the modem goes off-hook and the intrusion detection algorithm begins. This register has 250 ms increments, and the default value is 4 (1 sec).

Bit 11 (HOI) determines whether the host or modem responds to an intrusion. HOI = 0 (default) prevents the modem from hanging-up in response to an intrusion without host intervention. In this case, the host monitors U70 [2] (PPD) and takes the appropriate action when PPD is asserted indicating an intrusion. If HOI = 1, the modem hangs up immediately and will not go off-hook and dial when an intrusion is detected without host intervention. If %VN commands are set, HOI also causes the LINE IN USE result code upon PPD interrupt.

Bit 9 (AOC) = 0 (default) disables AutoOvercurrent. If enabled and an overcurrent condition is detected, the dc termination switches to 800 Ω, thus, reducing the current. If AOC = 0, the overcurrent condition is only reported by U70 [3] (OCD).

Bits 8:0 (OHT) set the delay between the time the modem goes off-hook and LVCS is read for an overcurrent condition. The default value for this register is 30 ms (see Table 75).

U78 is a bit-mapped register that controls intrusion detection blocking and intrusion suspend. U78 resets to 0x0000 with a power-on or manual reset (see Table 76).

Bits 15:14 (IB) controls intrusion blocking after dialing has begun. Table 76 defines the bit values and intrusion blocking.

Bits 7:0 (IS) set the delay between the start of dialing and the start of the intrusion algorithm when IB = 10 (see Table 76).

			Table 75. U77 Bit Map
Bit	Name	Function
15:12	IST	Intrusion Settling Time (250 ms units) 1 second default.
11	HOI	Hang-Up On Intrusion.
		0	= ISOmodem does not automatically hang up after an off-hook PPD interrupt.
		1	= ISOmodem automatically hangs up after an off-hook PPD interrupt.
10	Reserved	Read returns zero.
9	AOC	AutoOvercurrent.
		0	= Disable.
		1	= Enable.
8:0	OHT[8:0]	Off-Hook Time (1 ms units) 30 ms default.

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