SI2493-C-GT Silicon Laboratories Inc, SI2493-C-GT Datasheet - Page 27

• Manufacturer Part Number: SI2493-C-GT
• Description: IC ISOMODEM SYSTEM-SIDE 24TSSOP
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2493-C-GT

• Mfg Application Notes: SI2493/57/34/15/04, Appl Note AN93
• Data Format: V.21, V.22, V.23, V.29, V.32, V.34, V.90, V.92, Bell 103, Bell 212A
• Baud Rates: 56k
• Interface: Parallel
• Voltage - Supply: 3 V ~ 3.6 V
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

the <EM> <mark> indicator if the sending modem
experienced a transmitter underrun or overrun problem.
In general, the RTS flow control is not used. However, if
it is used, and if RTS is negated for too long, the receive
buffers will eventually overflow. This is called a receiver
overrun, and the modem sends an <EM> <rover>
indicator. A receiver overrun is considered to be a
catastrophic failure, and the host is expected to
terminate the session. Host software must be designed
so that an <EM> <rover> indicator does not occur.
It is expected that the <EM> <rover> indicator be
encountered during system debug, and designing the
system software properly to avoid having these
indicators occur should be the design goal.
Please note that there is an option available in the
U87[10]. The reason for this option is to determine what
the modem sends to the DTE when the modem
receives back-to-back occurrences of the special
characters, 0x19, 0x99, 0x11, and 0x13, at the DCE.
As an example, if the following string is received at the
DCE:
<0x19> <0x19> <0x11> <0x11>
If U87[10] = 0, this is what the host software will receive
at the DTE:
<0x19> <0x5D> <0x19> <0xA2>
If U87[10] = 1, this is what the host software will receive
at the DTE:
<0x19> <0x5C> <0x19> <0x5C> <0x19> <0xA0>
<0x19> <0xA0>
The choice of how to program U87[10] is based on
whether or not it is desired to simplify the host receive
parsing algorithm or to guarantee that the receive
throughput is not overly affected by the <EM>
<shielding>. In the worst case, if there is a large frame
consisting only of special characters, the required
throughput at the DTE will have to be at least 2x that of
the DCE rate to account for the <EM> shielding
overhead.
There are two methods of ending a call. One is to use
the <EM> <eot> command followed by an ATH. Note
that sending the <EM> <eot> command will cause the
modem to go to command mode and stop the
transmitter; however, the modem does not go back on
hook until the ATH.
The other method is to use the <EM> <esc> command
to escape to command mode, and then issue an ATH
command. The main difference being that the <EM>
<esc> does not shut off the transmitter. The <EM>
<esc> can also be followed by an ATO command if it is
desired that the connection be resumed.
Rev. 0.9
3.1.8. AT Command Set
AT commands begin with the letters AT, end with a
carriage return, and are case-insensitive. However,
case cannot be mixed in a single command. The only
exception to this format is the A/ command. This
command is neither preceded by AT nor followed by a
carriage return but re-executes the previous command
immediately when the “/” character is typed. Generally,
AT commands can be divided into two groups: control
commands and configuration commands. Control
commands, such as ATD, cause the modem to perform
an action (in this case, dialing). The value of this type of
command is changed at a particular time to perform a
particular
“ATDT1234<CR>” causes the modem to go off-hook
and dial the number 1234 via DTMF. No change is
made to the modem settings during the execution of an
action command.
Configuration
characteristics until they are modified or reversed by a
subsequent configuration command or the modem is
reset. Modem configuration status can be determined
with the use of ATY$, ATSn?, or AT:Rhh commands
where Y is a group of AT command arguments, n is an
S-register number (decimal), and hh is the hexadecimal
address of a U-Register.
The AT commands for reading configuration status are
listed in Table 14. Each command is followed by a
carriage return.
The examples in Table 15 assume the modem is reset
to its default condition. Each command is followed by a
carriage return.
ATY$ settings
Command
AT+VCID?
AT:Rhh
ATSn?
AT%$
AT&$
ATS$
AT\$
AT:R
AT$
Table 14. Configuration Status
action.
commands
Displays status of a group of
settings.
Basic AT command settings.
AT& command settings.
AT% command settings.
AT\ command settings.
Displays contents of S-Register n
Displays contents of all S-Registers
Displays contents of U-Register hh
Displays the current contents of all
U-Registers.
Displays caller ID setting.
For
example,
Action
change
the
AN93
command
modem
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