SI2457-D-FS Silicon Laboratories Inc, SI2457-D-FS Datasheet - Page 91

• Manufacturer Part Number: SI2457-D-FS
• Description: IC ISOMODEM SYSTEM-SIDE 16SOIC
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2457-D-FS

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

5.7. U Registers
U registers (user-access registers) are 16-bit registers written by the AT:Uhh command and read by the AT:R (read
all U registers) command or AT:Rhh (read U-register hh) command. See the AT command list in Table 39 on
page 59. All values associated with the U registers, the address, and the value written to or read from the register
are hexadecimal.
Some U registers are reserved and not available to the user. Therefore, there are gaps in the available U-register
address sequence. Additionally, some bits within available U registers are reserved. Any attempt to write to a non-
listed U register or to write a reserved bit can cause unpredictable modem operation.
There are two types of U registers. The first represents a single 16-bit term, such as a filter coefficient, threshold,
delay, or other quantity. These registers can be read from or written to as a single 16-bit value. The second type of
U register is bit mapped. Bit-mapped registers are also written and/or read in hexadecimal, but each bit or
combination of bits in the register represents an independent value. These individual bits are used to enable or
disable features and indicate states. Bits in these registers can be read/write, read only, reserved, or they may be
required to always be set to a certain value. Pay particular attention when writing to bit-mapped registers to ensure
no reserved bits are overwritten. When changing bits in a U register with reserved bits, use a read-modify-write
procedure: read the register value with AT:R; modify only the desired bits, then write the new value with AT:U. This
will ensure the reserved bits are not altered. All U registers revert to their default settings after a reset.
The U registers can be broken into three groups: call progress (U0–U33, U49–U4C), dialing (U37–U48), line
interface, and extended functions (U4D–UA9). Table 46 lists the available U registers, a brief description, and their
default values. Table 47 summarizes the signals and values available in the bit-mapped registers. Country-specific
register values are presented in "6.2. Country-Dependent Setup" on page 133. All default settings are chosen to
meet FCC requirements.
Register Address
U0A
U0B
U0C
U0D
U0E
U00
U01
U02
U03
U04
U05
U06
U07
U08
U09
0x000C
0x000D
0x000A
0x000B
0x000E
0x0000
0x0001
0x0002
0x0003
0x0004
0x0005
0x0006
0x0007
0x0008
0x0009
(Hex)
DT1A0
DT1B1
DT1B2
DT1A2
DT1A1
DT2A0
DT2B1
DT2B2
DT2A2
DT2A1
DT3A0
DT3B1
DT3B2
DT3A2
DT3A1
Name
Dial-tone detection filters stage 1 biquad coefficients.
Dial-tone detection filters stage 2 biquad coefficients.
Dial-tone detection filters stage 3 biquad coefficients.
Table 46. U-Register Descriptions
Rev. 1.3
Description
AN93
Default
0x00A0
0x6EF1
0xC4F4
0xC000
0x78B0
0xC305
0xB50A
0x0800
0x0000
0x0000
0x0000
0x0000
0x0000
0x00A0
0x4000
Value
91