Specifications
Chapter 1 – Universal Socket Connectivity
Multi-Tech Systems, Inc. Universal Socket Hardware Guide for Developers (S000342F) 15
Pin Signal
Name
In/Out Description
24 –RESET*
I
Device Reset (with pull-up). The active low –RESET input resets the device logic
and returns the configuration of the device to the original factory default values or
"stored values" in the NVRAM. –RESET is tied to VCC through a time-constant
circuit for “Power-on-Reset” functionality. The module is ready to accept commands
after a fixed amount of time (“X” Time) after power-on or reset.
Model Time Constant "X" Time Minimum Reset Pulse*
MT5600/5656SMI 250 ms 6 seconds 100us
MT5634/9234SMI 400 ms 6 seconds 100us
MT2456SMI-22 250 ms 6 seconds 100us
MT2456SMI-IP 250 ms 6 seconds 100us
MTXCSEM 250 ms 6 seconds 100us
MT100SEM 250 ms 6 seconds 100us
MT128SMI 200 ms 6 seconds 100us
MTSMC-G 250 ms 6 seconds 100us
MT800SWM 250 ms 6 seconds 100us
MTS2BTSMI 250 ms 6 seconds 100us
*The SocketModem device may respond to a shorter reset pulse.
Reset Line Interface for the MT5656SMI, MT2456SMI, MT2456SMI-IP. The
modem’s reset line employs a .01uF cap and a 10K pull up resistor. Care must be
taken to ensure the system the modem is place into is not affected by the added
capacitance of the reset line. It is not advisable to use an open collector driver in the
embedded system's reset circuitry to drive a reset signal to the embedded modem
and other I.C.s in the customer’s design. Rather, if an open collector driver is to be
used, run that output to the modem only and use a separate driver for other
embedded components. The modem’s reset signal may also be driven by a circuit
that both sinks and sources current if desired.
It is also important to note that these modems do not require an external reset. They
have their own internal reset circuitry and voltage monitor and will function correctly
even if the reset input is open.
Reset GPRS and CDMA (MTSMC-G and MTSMC-C). This signal is used to force a
reset procedure by providing low level during reset of at least 500us. The signal is
considered an emergency reset only. A reset procedure is already driven by internal
hardware during the power-up sequence. If no external reset is necessary, this input
can be left open. If used (emergency reset), it has to be driven by an open collector
or an open drain.
Reset EDGE with pull-up (MTSMC-E). The active low –RESET input resets the
device logic and returns the configuration of the device to the original factory default
values of "stored values" in the NVRAM. –RESET is tied to VCC through a time-
constant circuit for “Power-on-Reset” functionality. The module is ready to accept
commands after a fixed amount of time after power-on or reset.
25
USB_VBUS I
USB Voltage Sense. Senses the voltage level of the USB to determine if the bus is
available.
26
GND GND
Logic Ground.
27
USB_DP I/O
USB Data Positive. Positive pin of the USB data pair.
27
USB_DN I/O
USB Data Negative. Negative pin of the USB data pair.
29
LED DCD O
DCD (Active High). Output from 74LCX14 with a 1000 Ohms resistor in series.
SocketWireless Bluetooth (MTS2BTSMI): When lit, indicates a connection. No
series resistor.
30
LED RX O
RX (Active High). Output from 74LCX14 with a 1000 Ohms resistor in series.
SocketWireless Bluetooth (MTS2BTSMI): No series resistor.
31
LED DTR O
DTR (Active High). Output from 74LCX14 with a 1000 Ohms resistor in series.
SocketWireless Bluetooth (MTS2BTSMI): No series resistor.
32
LED TX O
TX (Active High). Output from 74LCX14 with a 1000 Ohms resistor in series.
SocketWireless Bluetooth (MTS2BTSMI): No series resistor.
33
–RTS I
Request to Send (Active Low). –RTS is controlled by the DTE to indicated whether
or not the DTE is ready to receive data. –RTS ON (low) indicates that the DTE is
ready to receive data from the modem on RXD. –RTS OFF indicates to the module
that it should not transfer data on the RXD.
In the command state, the modem ignores –RTS.
Note: When the –RTS pin is not in use, it should be tied low.
* RESET – A Design Consideration: Allowing the host processor to control the RESET line of the module provides
the benefit of allowing the host to reset the device in the event of a failure to respond normally. Resetting the module
will return it to a known functional state.