User's Guide

Review Copy 11-6-10
ThingMagic Micro Family Guide
5
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USB Interface
Supports USB 2.0 full speed device port (12 Megabits per second) using the three USB pins (USB_DM,
USB_DP, and USB_5VSENSE). Do not tie the USB_5VSENSE to a 5V power source, as this will prevent
the interface from detecting when the USB interface is connected or disconnected.
General Purpose Input/Output (GPIO)
The two GPIO connections, provided through the Micro Digital Connector Signal Definition, may be
configured as inputs or outputs using the MercuryAPI. In the module, the GPIO pins connect through 100
ohm resistors to the high current PA0 and PA1 pins of the AT91SAM7S processor. Consult the Micro
Specifications for additional details.
Pins configured as inputs must not have input voltages that exceed voltage range of -0.3 volts to +5.5 volts.
In addition, during reset the input voltages should not exceed 3.3V.
Outputs may source and sink 16 mA. Voltage drop in the internal series 100 ohm resistor will reduce the
delivered voltage swing for output loads that draw significant current.
Input Mode
• TTL compatible inputs
• Logic low < 0.8 V
• Logic high > 2.0V
• 5V tolerant
Output Mode
• 3.3 Volt CMOS Logic Output with 100 ohms in series
• Greater than 1.9 Volts when sourcing 8 mA
• Greater than 2.9 Volts when sourcing 0.3 mA
• Less than 1.2 Volts when sinking 8 mA
• Less than 0.2 Volts when sinking 0.3 mA
Module power consumption can be adversely affected by incorrect GPIO configuration. Similarly, the power
consumption of external equipment connected to the GPIOs can also be adversely affected. The following
instructions will yield specification compliant operation.
On power up, the Micro module configures its GPIOs as inputs to avoid driving current into circuitry that
may not be prepared for this. The input configuration is as a 3.3 volt logic CMOS input and will have a
leakage current not in excess of 400 nA. The input is in an undetermined logic level unless pulled externally
to a logic high or low. Module power consumption for floating inputs is unspecified. With the GPIOs
configured as inputs and individually pulled externally to either high or low logic level, module power
consumption is as listed in the Micro Power Consumption table.
GPIOs may be reconfigured individually after power-up to become outputs. This configuration takes effect
either at API execution or a few tens of milliseconds after power up if the configuration is stored in
nonvolatile memory. The automated configuration into outputs is prevented if the module is held in the boot
loader by Reset Line being held low. Lines configured as outputs consume no excess power if the output is
left open. Specified module power consumption is achieved for one or more GPIO lines set as output and