ThingMagic Micro Hardware - Manual (Page 24)

Hardware Interfaces
A D I V I S I O N O F T R I M B L E
24 Hardware Overview
USB Interface
Supports USB 2.0 full speed device port (12 Megabits per second) using the two USB
pins (USB_DM and USB_DP).
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. The GPIO pins connect
through 100 ohm resistors to the high current PA0 and PA1 pins of the AT91SAM7S
processor. The processor data sheet can be consulted 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 contention from
user equipment that may be driving those lines. 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