Specifications

Chapter 1 – Universal Socket Connectivity
Multi-Tech Systems, Inc. Universal Socket Hardware Guide for Developers (S000342I) 15
Pin Signal Name In/Ou
t
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 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*
MT5600/5656SMI 250 ms 6 seconds 100us
MT9234SMI 400 ms 6 seconds 100us
MT2456SMI-22 250 ms 6 seconds 100us
MT100SEM 250 ms 6 seconds 100us
MTSMC-G 250 ms 6 seconds 100us
MTSMC-H 250 ms 10 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 and MT2456SMI. 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 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 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 T
X
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 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.