Low cost programmable hvac controller having limited memory resources

A programmable HVAC controller having non-volatile memory and random-access memory (RAM), wherein the non-volatile memory has at least two portions, a first portion for storing firmware and a second portion that is user programmable, comprising:

• a function block engine resident in the first portion of the non-volatile memory;
• a block execution list resident in the second portion of the non-volatile memory;
• and
• a parameter and/or variable storage space resident in the RAM;
• wherein the block execution list is field programmable.

A method of operating a HVAC controller having non-volatile memory and random-access memory (RAM), the method comprising:

• storing a list of function blocks in non-volatile memory;
• executing a program according to the configured list of function blocks;
• when executing a function block:
• executing the function blocks from the non-volatile memory;
• reading variables stored from the RAM;
• and
• writing values to the RAM.

A HVAC controller having non-volatile memory and random-access memory (RAM) comprising:

• one or more execution modules resident in the non-volatile memory;
• one or more application configuration modules resident in the non-volatile memory;
• and
• a parameter storage space resident in the RAM;
• wherein one or more execution modules execute at least one program from the non-volatile memory;
• wherein the one or more application configuration modules are field programmable.