NAL Research Corporation (TN2009-25-V1.0)
8
‗/‘ position. A flathead screw driver can be used to turn the rotary switches to change from serial to USB and
vice versa.
A standard USB port 2.0 comprises of four pins as shown in Table 1. When the rotary switches are set
for USB, pin 9 of the multi-interface connector is assigned to USB D , pin 13 is assigned to USB D+ and pin
19 is assigned to USB VBUS. Any of the signal ground pins (14, 23 or 25) can be used as USB ground. USB
driver for the A3LA-XM can be found on the CD provided in the same package of the modem. Figure 3 shows
the pin assignments for a standard USB connector, which can be used to fabricate a USB interface cable
between the A3LA-XM DB25 connector and a DTE USB connector.
IMPORTANT:
User can remove the A3LA-XM‘s bottom plate to toggle the RS232/USB rotary
switches but not for repair or services. The warranty is voided if the A3LA-XM is disassembled for
any reason other than to set these switches.
IMPORTANT:
The A3LA-XM USB port does not work reliably under Windows Vista 64.
3.4 DC Power Interface
The DC power input is through pins 4 & 16 (EXT_B+) and pins 3 & 17 (EXT_GND). Note that two pins (4
and 16) are provided for the external (EXT_B+) DC input. Two pins (3 and 17) are also provided for the
associated external (EXT_GND) ground input. This is done to distribute the current across two wires, and
therefore all four pins should be utilized in the external power connection. The DC power requirements for
the A3LA-XM are summarized on page 5.
The A3LA-XM will automatically turn on/off when external DC power is applied/removed via the EXT_B+
and EXT_GND inputs. The EXT_ON_OFF (pin 1) control input is used to turn a powered A3LA-XM on and off
in a toggle fashion. The EXT_ON_OFF control input is normally ―floating‖ (i.e. high). When it is pulled to GND
Figure 2.
Location of the rotary switches on the A3LA-XM.
1 2 3 4
VBUS D
GND
D
Figure 3.
Pin assignments for a standard USB connector.
Rotary Switches
