Silicon Laboratories SI2493/57/34/15/04, SI2494/39 manual U68 Bit Map

AN93

	Table 67. U67 Bit Map* (Continued)
Bit Name	Function

0RT Ringer Threshold Select.

Used to satisfy country requirements on ring detection. Signals below the lower level do not generate a ring detection; signals above the upper level are guaranteed to generate a ring detection.

0 = 11 to 22 Vrms.

1 = 17 to 33 Vrms.

U68 is a bit-mapped register with bits 15:3 reserved. Reading these bits returns zero. Bits 4 and 2:0 are all read/ write (see Table 68).

Bit 2 (BTE) = 0 (default) is disabled by default. When BTE = 1, the DAA automatically responds to a collapse of the line-derived power supply during a billing tone event. When off-hook, if BTE = 1 and BTD goes high, the dc termination is increased to 800 Ω to reduce loop current. If BTE and U70 [9] (RIM) are set to 1, an interrupt from U70 [1] (RI) also occurs when BTD goes to 1 (high).

Bit 1 (ROV) is normally 0 and is set to 1 to report an excessive receive input level. ROV is cleared by writing it to 0. Bit 0 (BTD) = 0 normally but is set to 1 if a billing tone is detected. BTD is cleared by writing a 0 to BTD.

U68 resets to 0x0000 with a power-on or manual reset.

U6A is a bit-mapped register with bits 15:3 and 1:0 reserved. Reading these bits returns zero. Bit 2 is read-only (See Table 69).

Bit 2 (OVL) is a read-only bit that detects a receive overload. This bit is similar to U68 [1] (ROV) except OVL clears itself after the overload condition is removed.

			Table 68. U68 Bit Map*
Bit	Name	Function
15:8	Reserved	Read returns zero.
7:3	Reserved	Do not modify.
2	BTE	Billing Tone Protect Enable.
		0	= Disabled.
		1	= Enabled.
1	ROV	Receive Overload.
		0	= Normal receive input level.
		1	= Excessive receive input level.
0	BTD	Billing Tone Detected.
		0	= No billing tone.
		1	= Billing tone detected (cleared by writing 0).

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