SI2493-D-FS Silicon Laboratories Inc, SI2493-D-FS Datasheet - Page 260

• Manufacturer Part Number: SI2493-D-FS
• Description: IC ISOMODEM SYSTEM-SIDE 16SOIC
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2493-D-FS

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

AN93
The ISOmodem in EPOS Applications
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The Rev D Si2493/57/34/15/04 and Rev A Si2494/39 include all Rev B and C patches.
AT:U87 [10] must be set when using Rev B silicon.
A V.80 interface to V.29 Fast Connect is not supported on Rev B silicon and can be accomplished only as a
patch on Rev C. Please contact Silicon Laboratories, Inc. for latest patch. "5.8. Firmware Upgrades" on page
121 outlines how to use this patch.
When operating as V.22 Fast Connect (+MS=V22, AT:U7A,3), the register U80 can be modified to account for
unusual server timings. The value in U80 should reflect the expected answer tone duration of the NAC. The
units are in 1/600 s. For example, if the answer tone duration of the server is 500 ms, AT:U80,012C.
When operating as V.22 Fast Connect (+MS=V22, AT:U7A,3), a short answer tone of at least 300 ms is required
for proper operation. This answer tone can be 2100 Hz, 2225 Hz, or a V.22 Unscrambled Binary Ones (USB1).
If the server NAC does not have any of these answer tones prior to scrambled data or HDLC flags, it is possible
to command the modem to operate without these tones by setting bit 15 of U80. The modem then begins
transmitting scrambled data (or HDLC Flags) some time after the end of dialing, based on the value in
U80 [14:0]. The units are in 1/600 s. For example, to command the modem to begin transmitting 3 s after the
end of dialing, set AT:U80,8708.
Block
Data
Block
Data
Data
Block
Data
Block
Data
Block
Data
Block
Figure 51. ISOmodem V.80 Protocol HDLC Framing in Framed Sub-Mode
RX frame, EM<ERR>
EM<FLAG> if good
if bad RX frame
between blocks
Transparency
Transparency
V.80 Handler
EM<FLAG>
Insert V.80
Encode
Decode
V.80
V.80
Transmit
Receive
UART
Path
Path
CTS*
RXD
TXD
MODEM
MODEM
UART
Rev. 1.3
UART
Add EM<FLAG>
Transparency
Transparency
or EM <ERR>
Isomodem with V.80
Decode
Encode
V.80
V.80
Frame Check
Detection
Sequence
Generate
HDLC
Insertion
FLAG
HDLC
FLAG
Zero-Bit
Deletion
Zero-Bit
Stuffing
g
n CRC
Check
RX Bit Clock
Demodulate
Modulate
Recovery
TX Bit
Clock
PLL
DCE
XTAL