Module Operation For The Programmable Variant - Digi XBee-PRO User Manual

Module operation for the programmable variant

Module operation for the programmable variant
The modules with the programmable option have a secondary processor with 32k of flash and 2k of RAM. This
allows module integrators to put custom code on the XBee module to fit their own unique needs. The DIN, DOUT,
RTS, CTS, and RESET lines are intercepted by the secondary processor to allow it to be in control of the data
transmitted and received. All other lines are in parallel and can be controlled by either the EM357 or the
MC9SO8QE micro (see Block Diagram for details). The EM357 by default has control of certain lines. These lines
can be released by the EM357 by sending the proper command(s) to disable the desired DIO line(s) (see XBee
Command Reference Tables).
In order for the secondary processor to sample with ADCs, the XBee VREF pin (27/SMT, 14/TH) must be connected
to a reference voltage.
Digi provides a bootloader that can take care of programming the processor over the air or through the serial
interface. This means that over the air updates can be supported through an XMODEM protocol. The processor
can also be programmed and debugged through a one wire interface BKGD (Pin 9/SMT, Pin 8/TH).
XBee/XBee-PRO ZigBee RF Modules User Guide 26