Multi-Tech Systems MT2456SMI22 - Manual (Page 7)

Chapter 2
-
Mechanical Specifications
Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 7
Pin Configurations
The MT2456SMI SocketModem with a serial interface use a 16-pin interface to provide an on-board DAA with tip
and ring connections, audio circuit for call-progress monitoring and serial interface via logic level signals.
Figure 2–2. Serial SocketModem Pins
Pin Descriptions
Pin
#
Signal
Name I/O
Type
Description
1 Tip I/O Tip Signal from Telco. Tip connection to the phone line (RJ11 Pin 3).
SocketModem is Tip/Ring is polarity insensitive.
2 Ring I/O Ring Signal from Telco. Ring connection to the phone line (RJ11 Pin 4).
SocketModem is Tip/Ring is polarity insensitive.
24 –RESET I Modem Reset (with weak pull-up). The active low –RESET input resets the
SocketModem logic and returns the AT command set to the original factory
default values or to "stored values" in NVRAM. –RESET is tied to VCC
through a 250 ms time constant circuit for "Power-on-Reset" functionality. The
modem is ready to accept commands within 6.5 seconds of power-on or reset.
Reset must be asserted for a minimum of 300 ns.
26 DGND Ground.
29 DCDIND DCD LED Indicator.
30 RXIND RXD LED Indicator.
31 DTRIND DTR LED Indicator.
32 TXIND TXD LED Indicator.
33 –RTS I Request to Send. RTS signal is used for hardware flow control.
34 –RXD O Received Data. Used to send data received from the telephone line and also
modem responses to the DTE. Modem response take priority over incoming
data. When no data is transmitted, the signal is held in mark condition.
35 –TXD I Transmit Data. The DTE uses this line to send data to the modem for
transmission over the telephone line or to transmit commands to the modem.
The DTE should hold this circuit in the mark state when no data is being
transmitted or during intervals between characters.