Specifications

AN93
Rev. 0.8 19
Figure 9. Si2493/57/34/15/04 Functional Block Diagram
Controller
The controller provides several vital functions including
AT command parsing, DAA control, connect sequence
control, DCE (data communication equipment) protocol
control, intrusion detection, parallel phone off-hook
detection, escape control, caller ID control and
formatting, ring detect, DTMF (dual tone multi-
frequency) control, call progress monitoring, error
correction, and data compression. The controller also
writes to the control registers that configure the modem.
Virtually all interaction between the host and the modem
is done via the controller. The controller uses “AT”
(ATtention) commands, S-Registers, and U-Registers to
configure and control the modem.
Data Compression
The modem can achieve DTE (host-to-ISOmodem)
speeds greater than the maximum DCE (modem-to-
modem) speed through the use of a data compression
protocol. The compression protocols available are the
ITU-T V.44, V.42bis, and MNP5 protocols. Data
compression attempts to increase throughput by
compressing the information to be sent before actually
sending it. The modem is thus able to transmit more
data in a given period of time. Table 9 details the
Si2493/57/34/15/04 error correction and data
compression modes of operation.
Serial
Interface/
UART
Parallel
Interface
DSP
DAA
Interface
ROM
PLL
Clocking
XTI XTO
CLKOUT
INT
RESET
C1
To Phone
Line
AOUT
Data Bus
Controller
Si3018/10
RXD
TXD
CTS
RTS
DCD
ESC
RI
CS
WR
RD
A0
D0-D7
Program Bus
RAM
EEPROM
Interface
EESD
EECLK
EECS
C2
Si3000
Interface
FSYNC
SDO
SDI
MCLK
Table 9. Enabling Error Correction/Data
Compression
To Enable Use AT Commands
V.44
1
V.42bis
V.42 (LAPM)
MNP5
MNP2–4
Wire
+DS44 (argument)
\N3 and %C1 (default)
V.42 and
V.42bis only
\N4 and %C1
V.42 only \N4 and %C0
MNP2-4 only \N2 and %C0
MNP2-5 only \N2 and %C1
No data compression and
no error correction
\N0 and %C0
Notes:
1. V.44 is available only on Si2493.