Silicon Laboratories SI2494/39, SI2493/57/34/15/04 manual U66 Bit Map, U67 Bit Map

AN93

Table 66. U66 Bit Map

Bit	Name	Function
15:7	Reserved	Read returns zero.
6	FDT	Frame Detect.
		0	= ISOcap frame lock not established
		1	= ISOcap frame lock established
5:0	Reserved	Read returns zero.

			Table 67. U67 Bit Map*
Bit	Name		Function
15:14	Reserved	Read returns zero.
13:12	MINI[1:0]	Minimum Operational Loop Current.
		Adjusts the minimum loop current at which the DAA can operate. Increasing the minimum oper-
		ational loop current can improve signal headroom at lower Tip-Ring voltages.
		MINI[1:0]	Min Loop Current
		00	10 mA
		01	12 mA
		10	14 mA
		11	16 mA
11:10	Reserved	Read returns zero

9ILIM Current Limiting Enable.

0 = Current limiting mode disabled.

1 = Current limiting mode enabled. This mode limits loop current to a maximum of 60 mA per the legacy TBR21 standard.

8 Reserved Read returns zero.

7DCR DC Impedance Selection.

0 = 50 Ω dc termination slope is selected. This mode should be used for all standard applications.

1 = 800 Ω dc termination is selected.

6OHS On-Hook Speed. See OHS2.

5:4	Reserved	Read returns zero.
3:2	DCV[1:0]	Tip-Ring Voltage Adjust.
		These bits adjust the voltage on the DCT pin of the line-side device, which affects the Tip-Ring
		voltage on the line. Low-voltage countries should use a lower Tip-Ring voltage. Raising the Tip-
		Ring voltage can improve signal headroom.
		DCV[1:0]	DCT Pin Voltage
		00	3.1 V
		01	3.2 V
		10	3.35 V
		11	3.5 V

1RZ Ringer Impedance.

0 = Maximum (high) ringer impedance.

1 = Synthesize ringer impedance. C15, R14, Z2, and Z3 must not be installed when setting this bit.

Rev. 1.3 109