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Part 1 
− Universal Socket Connectivity 
Chapter 1 – Universal Socket Connectivity 
Multi-Tech Systems, Inc. Universal Socket Hardware Guide for Developers (S000342M) 
13 
 
 
Pin 
Signal 
Name 
In/Out   Description
24 
–RESET* 
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 SocketModem 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* 
MTSMC-G2 
250 ms 
6 seconds 
100us 
MTSMC-C1 
250 ms 
3-15 seconds 
500us 
MTSMC-E1 
250 ms 
3-15 seconds 
500us 
MTSMC-H 
250 ms 
10 seconds 
100us 
MT9234SMI 
400 ms 
6 seconds 
100us 
MT5692SMI 
250 ms 
6 seconds 
100us  
MT2492SMI 
250 ms 
6 seconds 
100us 
MT100SEM-IP 
250 ms 
6 seconds 
100us 
MT810SWM-IP 
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 MT5692SMI. The modem’s reset line employs a 10K 
pull up resistor. 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-G2 and MTSMC-C1). This signal is used to 
force a reset procedure by providing low level during reset of at least 500usThe 
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-E1). 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. The SocketModem 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.  
28 
USB_DN I/O USB Data Negative. Negative pin of the USB data pair.  
29 
LED DCD 
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 
RX (Active High). Output from 74LCX14 with a 1000 Ohms resistor in series. 
SocketWireless Bluetooth (MTS2BTSMI): No series resistor. 
31 
LED DTR 
DTR (Active High). Output from 74LCX14 with a 1000 Ohms resistor in series. 
SocketWireless Bluetooth (MTS2BTSMI): No series resistor. 
32 
LED TX 
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 
SocketModem 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 SocketModem provides 
the benefit of allowing the host to reset the device in the event of a failure to respond normally. Resetting the SocketModem 
will return it to a known functional state. 
 
 
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