2.4.2 ID System Implementation on Extensions

The ID device that must be mounted on Xplained Pro extensions is the Atmel ATSHA204A in a single-wire configuration where the device is powered through the communication line. On the Atmel Xplained Pro extensions the device with the ordering code ATSHA204A-MAHCZ-T is used. Relevant features of the device are:

  • Operation voltage from 2.0V to 5.5V

  • Single wire interface

  • 8-lead UDFN (one wire)

  • Data area with 512 bytes

  • Configuration area with 88 bytes

  • One time programmable (OTP) area with 64 bytes

The example in Figure 2-6 shows the implemented ID circuitry on the Xplained Pro extension boards. The ID_DATA signal is routed to the Embedded Debugger where this signal is pulled-up. The ID chip is powered through the ID_DATA line through an internal diode between pin 5 and pin 8. R100 acts as a bleeding resistor to discharge C100 when the extension is unplugged, this is necessary in order to get the ID device in a safe state within a reasonable time before the board is plugged in again. The ID_DATA line is connected to a dedicated pin on the extension header your Xplained Pro board implements.

Figure 2-6. ID Device Circuitry