SI3015-FS Silicon Laboratories Inc, SI3015-FS Datasheet - Page 16

• Manufacturer Part Number: SI3015-FS
• Description: SI2400 ISOMODEM LINE-SIDE
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3015-FS

• Data Format: V.90
• Interface: Serial
• Voltage - Supply: 3.3 V ~ 5 V
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Baud Rates: -

Si2400
Note: TIES is not the recommended escape solution for the
Whether using an escape method or not, when the
carrier is lost, the modem will automatically return to
command mode and report “N”.
8-Bit Data Mode (8N1)
The 8-bit data mode is the default mode after power-up
or a reset and is set by SE0[3] (ND) = 0b. It is
asynchronous, full duplex, and uses a total of 10 bits
including a start bit (logic 0), 8 data bits, and a stop bit
(logic 1). Data received from the remote modem is
transferred from the Si2400 to the host on the RXD pin.
Data transfer to the host begins when the Si2400
asserts a logic 0 start bit on RXD. Data is shifted out of
the Si2400 LSB first at the DTE rate determined by the
SE0[2:0] (SD) setting and terminates with a stop bit.
16
Use the ESC pin—To program the GPIO3 pin to
function as an ESCAPE input, set GPIO3
SE2[5:4] = 11b. In this setting, a positive edge
detected on this pin will return the modem to
command mode. The “ATO” string can be used to re-
enter data mode.
Use 9-bit data mode—If 9-bit data format with
escape is programmed, a 1 detected on bit 9 will
return the modem to command mode. (See Figure 2
on page 9.) This is enabled by setting
SE0[3] (ND) = 1b and S15[0] (NBE) = 1b. The ATO
string can be used to reenter data mode. Ninth bit
escape does not work in the security modes.
Use TIES—The time independent escape sequence
is a sequence of three escape characters (“+”
characters by default). Once these characters have
been recognized, the modem enters the Command
state without sending a confirming result code to the
terminal. The modem then starts an internal prompt
delay timer. From that point on if an AT<CR>
(attention) command is received before the timer
expires, the timer is stopped and the “O” response
code is sent to the terminal. This indicates that the
Si2400 is in command mode.
If any other data is received while the timer is
running, the timer is stopped, the device returns to
the online state, and the data appearing on TXD is
sent to the remote modem.
If the timer expires, a confirming “O” response code
is sent to the terminal indicating that the modem is in
command mode.
TIES is enabled by writing register
S14[5] (TEO) = 1b. Both the escape character “+”
and the escape time-out period are programmable
via registers S0F (TEC) and S10 (TDT), respectively.
most robust designs. Any data string containing the
sequence “+++AT<CR>” will interrupt a data sequence
erroneously.
Rev. 1.1
Data from the host for transmission to the remote
modem is shifted to the Si2400 on TXD, beginning with
a start bit, LSB first at the DTE rate determined by the
SE0[2:0] setting and terminates with a stop bit. After the
middle of the stop bit time the Si2400 will begin looking
for a logic 1 to logic 0 transition signaling the start of the
next character on TXD to be sent to the line (remote
modem).
9-Bit Data Mode (9N1)
The 9-bit data mode is set by SE0[3] (ND) = 1b. It is
asynchronous, full duplex, and uses a total of 11 bits
including a start bit (logic 0), 9 data bits, and a stop bit
(logic 1). Data received from the line (remote modem) is
transferred from the Si2400 to the host on the RXD pin.
Data transfer to the host begins when the Si2400
asserts a logic 0 start bit on RXD. Data is shifted out of
the Si2400 LSB first at the DTE rate determined by the
SE0[2:0] (SD) setting and terminates with a stop bit.
Data from the host for transmission to the line (remote
modem) is shifted to the Si2400 on TXD, beginning with
a start bit, LSB first at the DTE rate determined by the
S-Register SE0[2:0] (SD) setting and terminates with a
stop bit. After the middle of the stop bit time the Si2400
will begin looking for a logic 1 to logic 0 transition
signaling the start of the next character on TXD to be
sent to the line (remote modem).
The ninth data bit may be used to indicate an escape by
setting S15[0] (NBE) = 1b. In this mode, the ninth data
bit will normally be set to 0 when the modem is online.
When the ninth data bit is set to 1, the modem will go
offline into Command mode and the next frame will be
interpreted as an AT command. Data mode can be
reentered using the ATO command.
Flow Control
No flow control is needed if the DTE rate and DCE rate
are the same. If the serial link (DTE) data rate is set
higher than the line (DCE) rate of the modem, flow
control is required to prevent loss of data to the
transmitter.
To control data flow, the clear-to-send (CTS) pin is used.
As shown in Figure 2 on page 9, the CTS pin will
normally be high, and will be low whenever the modem
is able to accept new data. The CTS pin will go high
again as soon as a start bit is detected on the TXD pin
and will remain high until the modem is ready to accept
another character.