Separate, but related, firmware programs for multiple microprocessor-controlled irrigation controllers that are interrelated in their control of irrigation within an irrigation system are generated off-line at a personal computer. The programs are downloaded into a transportable memory device that holds sixty-four separate programs. The memory device is transported to each irrigation controller and plugged to a digital communication channel. The device automatically identifies itself to the controller, and vice versa. The appropriate program is automatically uploaded from the device to the controller. The controller's old program and its historical irrigation record data is loaded into the device and delivered to the personal computer for validation and analysis. A wireless remote test command assembly, an extension maintenance panel, or a radio-link central module may be alternatively connected to the controller's digital communication channel. The controller is powered by the memory device during the uploading.