Specifications

AN93
Rev. 0.9 57
The reset recovery time (the time between a hardware
reset or the carriage return of an ATZ command and the
time the next AT command can be executed) is
approximately 300 ms.
There is no non-volatile memory on the Si2493/57/34/
15/04 other than Program ROM. When reset, the
Si2493/57/34/15/04 reverts to the original factory default
settings. Any set-up or configuration data and software
updates must be reloaded after every reset. This is true
whether the reset occurs due to a power-down/powerup
cycle, a power-on reset through a manual reset switch,
by writing U6E[4] (RST) = 1, or executing ATZ.
A suggested reset sequence is as follows:
1. Apply reset pulse to RESET
(Si2493/57/34/15/04,
pin 12); write RST bit or ATZ<CR>.
2. Wait > 300 ms.
3. Load firmware updates (if required).
4. Set non-default DAA interface parameters—DCV,
ACT, ILIM, OHS2, OHS, RZ, RT, (U67), LIM, (U68).
5. Set non-default cadence values—Busy Tone,
Ringback, Ring.
6. Set non-default frequency values—Ring.
7. Set non-default filter parameters.
8. Set non-default S-register (values).
The modem is now ready to detect rings, answer
another modem, call, or dial out to a remote modem.
Some key default settings for the modem after reset or
powerup include the following:
 Serial interface.
 V.92 and fall-backs enabled (Si2493).
 V.90 and fall-backs enabled (Si2457).
 V.34 and fall-backs enabled (Si2434).
 V.32bis and fall-backs enabled (Si2415).
 V.22bis and fall-backs enabled (Si2404).
 V.42/42bis enabled.
 “+++” escape sequence enabled.
 Answer-on-ring is disabled.
 Speaker off.
 DTE echo enabled.
 Verbal result codes enabled.
 CTS only enabled.
 FCC (US) DAA and call progress settings.
Review the AT command tables and register lists for
complete details on all default settings. AT commands
and register writes must be used to modify factory
defaults after every reset.
Table 24. Si2493/57/34/15/04 Pull-Downs and Features
Mode Pin4 Pin9 Pin10 Pin11 Pin15 Pin18 Pin23*
Serial, EEPROM, 27 MHz, Autobaud 0 1 X 1 1 1 0
Serial, EEPROM, 27 MHz, 19.2K DTE 0 1 X 1 1 0 0
Serial, EEPROM, 4.9152 MHz, Autobaud 0 1 X 1 1 1 1
Serial, EEPROM, 4.9152 MHz, 19.2K
DTE
01X1101
Serial, 27 MHz, Autobaud* 1 1 X 1 1 1 0
Serial, 27 MHz, 19.2K DTE 1 1 X 1 1 0 0
Serial, 4.9152 MHz, Autobaud* 1 1 X 1 1 1 1
Serial, 4.9152 MHz, 19.2K DTE 1 1 X 1 1 0 1
Parallel, 4.9152 MHz X 1 1 1 0 X X
Parallel, 27 MHz X 1 1 0 0 X X
*Note: 27 MHz is the only pulldown option available on the 16-pin devices and can be enabled with a pulldown
on pin 15 rather than pin 23.