Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 107)

AN93
Rev. 1.3 107
U63 (DAAC2) is a bit-mapped register with bits 3:0 reserved and should be modified through a read-modify-write
operation.
Bits 15:8 (LCS) function as an 8-bit unsigned measure of off-hook loop current with a resolution of 1.1 mA/bit.
Bits 7:4 (ACT) set the ac termination the Si3010/Si3018 presents to Tip and Ring. The ac impedance setting is
dictated by the certification requirements for the country in which the modem is used.
U65 (DAAC4) is a bit-mapped register with bits 3:0, 12:5, and 15 reserved. Bits 1:0 and 6:5 must not be changed.
Bit 14 (PWMG) = 0 (default) provides 0 dB gain to AOUT. PWMG = 1 provides a 6 dB gain to AOUT.
Bit 13 (PDN) = 0 enables the device for normal operation. PDN = 1 completely powers down both the Si3018/10
and the Si24xx chips. The bit takes effect at the carriage return of the AT command setting this bit high. Once this
bit is set, the modem must be reset via the RESET pin to become active. When reset, the modem reverts to the
default settings.
Bit 4 (PDL) = 0 (default) enables the device for normal operation. PDL = 1 powers the Si3018/10 down. This is a
test mode typically used for board-level debugging, not normal modem operation.
U65 resets to 0x00E0 with a power-on or manual reset.
4 Reserved Must be set to zero.
3 Reserved Must be set to zero.
2 FOH 0 = Automatic calibration timer set to 426 ms.
1 = Automatic calibration timer set to 106 ms.
1 DL 0 = Digital loopback beyond ISOcap interface.
1 = Digital loopback across ISOcap interface only.
0 Reserved Must be set to zero.
Table 64. U63 Bit Map
Bit Name Function
15:8 LCS Off-hook loop current (1.1 mA/bit).
7:4 ACT AC Termination Select
ACT AC Termination
0000 Real 600

0011 220
 + (820  || 120 nF) and 220  + (820  || 115 nF)
0100 370
 + (620  || 310 nF)
1111 Global complex impedance
3:0 Reserved Read returns 0011.
Table 65. U65 Bit Map
Bit Name Function
15 Reserved Read returns zero.
14 PWMG PWM gain.
0 = No gain.
1 = 6 dB gain applied to AOUT.
13 PDN Power Down.
0 = Normal.
1 = Power Down.
Table 63. U62 Bit Map (Continued)