SI3008-B-FS Silicon Laboratories Inc, SI3008-B-FS Datasheet - Page 14

• Manufacturer Part Number: SI3008-B-FS
• Description: IC ISOMODEM FCC LINE-SIDE 8SOIC
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3008-B-FS

• Data Format: V.22, V23, V.32, V.34, V.90, Bell 103, Bell 212A
• Baud Rates: 56k
• Interface: Parallel
• Voltage - Supply: 3 V ~ 3.6 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Product: Modem Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Si2401/Si3008
After the middle of the stop bit time, the Si2401 begins
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).
4.2.3. 9-Bit Data Mode (9N1)
The 9-bit data mode is set by SE0[3] (ND) = 1. 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 Si2401 to the host on the RXD pin.
Data transfer to the host begins when the Si2401
asserts a logic 0 start bit on RXD. Data is shifted out of
the Si2401 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 Si2401 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 Si2401
begins 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) = 1. In this mode, the ninth data bit
is normally set to 0 when the modem is online. When
the ninth data bit is set to 1, the modem goes offline into
command mode, and the next frame is interpreted as an
AT command. Data mode can be reentered using the
ATO command.
4.2.4. 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.
When CTS is asserted, the Si2401 is ready to accept a
character. While CTS is negated, no data should be
sent to the Si2401 on TXD. To simplify flow control, the
Si2401 has an integrated ten character transmit FIFO
and allows for two different CTS reporting methods. By
default, the CTS pin is negated as soon as a start bit is
detected on the TXD pin and remains negated until the
modem is ready to accept another character (see
Figure 2 on page 8.) By setting SFC7[7]=1 (CTSM),
CTS is negated when the FIFO is 70% full and is
reasserted when the FIFO is 30% full.
4.3. Low Power Modes
The Si2401 has three low-power modes:
14
DSP Powerdown. The DSP processor can be
powered down by setting register
Rev. 1.1
4.4. Parallel Phone Detection
The ISOmodem
telephone, modem, or other device is using the phone
line. This allows the host to avoid interrupting another
phone call when the phone line is already in use and to
intelligently handle an interruption when the ISOmodem
chipset is using the phone line.
4.4.1. On-Hook Intrusion Detection
When the ISOmodem chipset is sharing the telephone
line with other devices, it is important that it not interrupt
a call in progress. To detect when another device is
using the shared telephone line, the host can use the
ISOmodem chipset to monitor the TIP-RING dc voltage
with the LVS[7:0] bits (SDB). The LVS[7:0] bits have a
resolution of 1 V per bit with an accuracy of
approximately ±10%. Bits 0 through 6 of this 8-bit signed
2s complement number indicate the value of the line
voltage, and the sign bit (bit 7) indicates the polarity of
TIP and RING.
When all devices on a particular telephone line are on-
hook, there is no loop current flowing through TIP and
RING. Therefore, the voltage across TIP and RING is at
a maximum. (On most telephone lines, this on-hook
voltage is a minimum of 40 V.) Once a device goes off-
hook, current flows through TIP and RING on that
device, and the TIP-RING voltage drops appreciably.
(On most telephone lines, this off-hook voltage is a
maximum of 20 V.)
If the host checks the TIP-RING voltage via LVS before
causing the ISOmodem chipset to dial out or go off-
hook, the host can determine if another device is using
the telephone line. One way to do this is to verify that
the voltage represented in LVS is above some fixed
threshold, such as 30 V.
SEB[3] (PDDE) = 1.
In this mode, the serial interface still functions, and
the modem detects ringing and intrusion. However,
no modem modes or tone detection features
function.
Wake-Up-On-Ring. By issuing the ATZ command,
the Si2401 goes into a low-power mode where both
the microcontroller and DSP are powered down.
Only an incoming ring, a low TXD signal, or a total
reset will power up the chip again. Return from
wake-on-ring triggers the INT pin if S09[6]
(WOR) = 1 (WOR = 0
Total Powerdown. Setting SF1[5] = 1 and SF1[6] = 1
places the Si2401 into a total powerdown mode. All
logic is powered down including the crystal oscillator
and clock-out pin. Only a hardware reset can restart
the Si2401.
®
chipset is able to detect when another
b
by default).