The method is used for downloading firmware upgrades to a non-volatile memory (NVM) of a targeted remote programmable embedded field-deployed device over a communication network. The device is connected to the network and requires no human intervention at the remote site. The firmware includes a small upgrade program which performs programming tasks on the device according to commands received by the server. The method carried out by the upgrade program allows to upgrade the application program, the communication protocol stack, a set of mutable interrupt vector table or itself without the need of additional memory. It also has a bootstrap function which is responsible for verifying the integrity of the firmware upon reset of a device before transferring control to or back to the application program. Upgrades can be either server-initiated (the firmware provider pushes the new version out to the field) or device-initiated (the device pulls the latest firmware version from the server).