Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 109)

AN93
Rev. 1.3 109
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
9 ILIM 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.
7 DCR DC Impedance Selection.
0 = 50
 dc termination slope is selected. This mode should be used for all standard
applications.
1 = 800
 dc termination is selected.
6 OHS 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
1 RZ Ringer Impedance.
0 = Maximum (high) ringer impedance.
1 = Synthesize ringer impedance. C15, R14, Z2, and Z3 must not be installed when setting this
bit.