Maxim Integrated 73M2901CE AT Command - Manual (Page 21)

UG_2901CE_027 73M2901CE AT Command User Guide
Rev. 2.0 21
4 S-registers
The 73M2901CE allows the user to directly access the S-registers through the AT Command Set. This
feature enables an added level of control over the modem's operation. Setting S-registers directly
involves some amount of risk, and requires understanding of the internal function of the modem. The
order in which S-registers are set in the command string may be significant, for instance when setting S99
it is necessary that it be the first command in the command string because it affects many other
S-registers. The F command, which the restores factory defaults, voids any commands preceding it
including S-Register settings. AT commands themselves set S-registers so the user must be aware of
each operation remembering that each command in a command string is executed one at a time in the
order they are presented in the command string. The AT Command interpreter can set and reverse the
commands, giving a result far from what was intended; the modem assumes that the user knows what he
or she is doing.
4.1 Setting S-registers
The mechanism for directly setting an S-Register is the ATS[n] = [value] command. Where [n] is equal to
the particular S-Register, and [value] is equal to the value that is to be written to the register. The [value]
may be in either decimal or hex. Hexadecimal values must be preceded with a $ and must be two digits,
for example ATS14 = $A is not valid, but ATS14 = $0A is.
4.2 Reading S-registers
The mechanism for reading an S-Register is the ATS? or the ATS$ command. ATS? with result in a
decimal value reported to the DTE and ATS$ will result in a hexadecimal value being reported to the
DTE. The user should be aware that many registers have bits that are used internally and are constantly
changing in the idle state.
4.3 Setting/Reading S-registers While in Online Command Mode
While connected, it is possible to enter online command mode and Set or Read some S-registers. This may
not always produce the desired effect. Some S-register settings will not take effect until after the connection
has been broken. For example you would not be able to change modulation standards or go from
synchronous to asynchronous mode while connected. In addition values read from some S-registers while
in online command mode may not accurately reflect certain states.
4.4 S-registers Definitions
4.4.1 S0 – AutoAnswer
(Default = 0)
This register specifies the ring on which the modem will answer. A value of 1 to 255 will place the modem
in auto-answer mode and cause it to answer on the ring set by S0. A value of zero will disable
auto-answer.
RI will toggle after each ring cycle is qualified, the timing determined by the setting of the
S53 minimum ring off time register and the DTE data rate. The RI signal duration will be 60ms plus the
time to output the “RING” result code.
RING "ON"
TIME
RING "OFF" TIME
RING
RI
S0 is cleared on Reset.