Why is it called Thumb instruction set?

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Why is it called Thumb instruction set?

Thumb instructions are each 16 bits long, and have a corresponding 32-bit ARM instruction that has the same effect on the processor model. Thumb instructions operate with the standard ARM register configuration, allowing excellent interoperability between ARM and Thumb states.

Q. What is the difference between Thumb and Thumb 2 instruction set?

Thumb-2 is a superset of the Thumb instruction set. Thumb-2 introduces 32-bit instructions that are intermixed with the 16-bit instructions. The Thumb-2 instruction set covers almost all the functionality of the ARM instruction set.

Q. What are Thumb instructions?

Thumb instructions are each 16 bits long, and have a corresponding 32-bit ARM instruction that has the same effect on the processor model. Thumb instructions operate with the standard ARM register configuration, allowing excellent interoperability between ARM and Thumb states.

The 32-bit execution state supports two different instruction sets: T32 (“Thumb”) and A32 (“ARM”). The 64-bit execution state supports only one instruction set – A64. All A64, like all A32, instructions are 32-bit (4 byte) in size, requiring 4-byte alignment.

Q. What is the bit size of Thumb instruction?

Thumb instructions are either 16 or 32 bits long. Instructions are stored half-word aligned. Some instructions use the least significant bit of the address to determine whether the code being branched to is Thumb code or ARM code.

Q. What is the difference between Cortex-M3 and Cortex M4?

The Cortex-M3 and Cortex-M4 are very similar cores. Each offers a performance of 1.25 DMIPS/MHz with a 3-stage pipeline, multiple 32-bit busses, clock speeds up to 200 MHz and very efficient debug options. The significant difference is the Cortex-M4 core’s capability for DSP.

Q. What is the difference between ARM instruction and Thumb instruction?

ARM instructions are 32 bits wide. Thumb instructions are 16 or 32-bits wide. The ARM instruction set is a set of 32-bit instructions providing a comprehensive range of operations. The Thumb instruction set provides better code density, at the expense of performance.

The Thumb instruction set consists of 16-bit instructions that act as a compact shorthand for a subset of the 32-bit instructions of the standard ARM. When it’s operating in the Thumb state , the processor simply expands the smaller shorthand instructions fetched from memory into their 32-bit equivalents.

Q. What does ARM stand for?

Advanced RISC Machines
ARM (stylised in lowercase as arm, previously an acronym for Advanced RISC Machines and originally Acorn RISC Machine) is a family of reduced instruction set computing (RISC) architectures for computer processors, configured for various environments.

Q. What is² Thumb-2?

² Thumb-2 is an expansion of an earlier instruction set known unsurprisingly as Thumb. (Exercise: Why didn’t they call it Thumb-1?) The idea of using a 16-bit instruction set came from the SuperH, and ARM licensed it from Hitachi for use in Thumb mode.

Q. What is Thumb-2 mode encoding?

The Thumb-2 mode instruction encoding is variable-length, with a mix of 16-bit instructions and 32-bit instructions. Every instruction is required to begin on an even address, but 32-bit instructions are permitted to straddle a 4-byte boundary.

Q. Why is ARM Thumb-2 using 16-bit instruction set?

The idea of using a 16-bit instruction set came from the SuperH, and ARM licensed it from Hitachi for use in Thumb mode. ³ The use of r13 as the stack pointer is not architectural in classic ARM, but it is architectural in Thumb-2. Doing so frees up space in the tight 16-bit instruction encoding space.

Q. What is Thumb-2 mode in winwindows?

Windows uses the ARM in a mode known as Thumb-2 mode.² In Thumb-2 mode, some classic features are not available, such as most forms of predication. The Thumb-2 mode instruction encoding is variable-length, with a mix of 16-bit instructions and 32-bit instructions.

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