Stack processor using a ferroelectric random access memory (F-RAM) for code space and a portion of the stack memory space having an instruction set optimized to minimize processor stack accesses
A stack processor and method implemented using a ferroelectric random access memory (F-RAM) for code and a portion of the stack memory space having an instruction set optimized to minimize processor stack accesses and thus minimize program execution time. This is particularly advantageous in low power applications and those in which the power supply is only available for a finite period of time such as RFID implementations. Disclosed herein is a relatively small but complete set of instructions enabling a multitude of possible applications to be supported with a program execution time that is not too long.
1. A method for operating a stack processor comprising:
a data POP wherein data is transferred from a bottom portion of a data stack to a top portion of the data stack in a first cycle of the stack processor, wherein the top portion of the data stack is in a volatile memory in a Forth core in the stack processor and the bottom portion of the data stack is in a ferroelectric random access memory in the stack processor, separate from the Forth core and coupled to the Forth core by a single code/data bus extending between the Forth core and ferroelectric random access memory only, and wherein data is transferred from the bottom portion of the data stack to the top portion of the data stack through the single code/data bus;
transferring data from the top portion of the data stack to a top portion of a return stack in a second cycle of the stack processor, wherein the top portion of the return stack is a single register in the volatile memory, and wherein transferring data between the top portion of the data stack and the top portion of the return stack comprises copying data in the top portion of the data stack to the top portion of the return stack; and
a return PUSH wherein data is transferred from the top portion of the return stack to a bottom portion of the return stack in a third cycle of the stack processor, wherein the bottom portion of the return stack is in the ferroelectric random access memory, and wherein data is transferred from the top portion of the return stack to the bottom portion of the return stack through the single code/data bus,
wherein the first, second and third clock cycles are sequential, and wherein the data POP, return PUSH and the transferring data are performed in response to a stack-based computer programming language.
2. The method of claim 1 wherein the stack-based computer programming language comprises 64 possible instructions based upon a 16 bit word, wherein each of the instructions in the 16 bit word comprises 3 five bit instructions and a 16 th bit applicable to each of the 3 five bit instructions.
3. A method for operating a stack processor comprising:
in a first cycle of the stack processor transferring data from a bottom portion of a data stack to a top portion of the data stack, wherein the bottom portion of the data stack is in a ferroelectric random access memory (F-RAM) and the top portion of the data stack is in a volatile memory in a Forth core in the stack processor, and the data is transferred through a single code/data bus coupled between the F-RAM and the Forth core only;
in a second cycle of the stack processor copying the data from the top portion of the data stack to a top portion of a return stack, wherein the top portion of the return stack comprises a single register in the volatile memory; and
in a third cycle of the stack processor transferring the data from the top portion of the return stack to a bottom portion of the return stack, wherein the bottom portion of the return stack is in F-RAM and the data is transferred through the single code/data bus.
4. The method of claim 3 wherein the transferring and the copying of data are performed in response to a stack-based computer programming language supporting Forth core instructions.
5. The method of claim 4 wherein the Forth core instructions comprise 64 possible instructions based upon a 16 bit word, wherein each of the instructions in the 16 bit word comprises 3 five bit instructions and a 16th bit applicable to each of the 3 five bit instructions.
6. A method for operating a stack processor comprising:
transferring data from a bottom portion of a data stack to a top portion of the data stack, wherein the bottom portion of the data stack is in a ferroelectric random access memory (F-RAM) and the top portion of the data stack is in a volatile memory in a Forth core in the stack processor and the data is transferred through a single code/data bus coupled between the F-RAM and the Forth core only;
copying data from the top portion of the data stack to a top portion of a return stack, wherein the top portion of the return stack comprises a single register in the volatile memory; and
transferring the data from the top portion of the return stack to a bottom portion of the return stack, wherein the bottom portion of the return stack is in F-RAM and the data is transferred through the single code/data bus,
wherein the transferring and the copying of data are performed in three sequential clock cycles of the stack processor in response to Forth core instructions.
7. The method of claim 6 wherein the Forth core instructions comprise 64 possible instructions based upon a 16 bit word, wherein each of the instructions in the 16 bit word comprises 3 five bit instructions and a 16th bit applicable to each of the 3 five bit instructions.