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Hello,
We're considering an ARM based MCU as an alternative target to an existing 8051 based product, which leads me to ask some questions regarding the ARM architecture-
My understanding is that the ARM core has a 32 bit instruction set (typically), so asssuming a direct port of our existing 8051 code (8 bit instruction set) was possible, what would the expected size of program code be for the ARM target relative to that of the 8051 (bigger/smaller/indeterminate)?
Assuming it's possible for ARM based devices to fetch instructions from external flash (?), are there specific features that should be considered mandatory if the ARM device doesn't feature sufficient 'on-board' flash for program code/NVRAM (AMBA bus/SPI etc)?
Also if there's a resource that someone's aware of which deals with this level of detail, I'd appreciate a link, and any other comments/caveats regarding the ARM core...
Many thanks
David
what would the expected size of program code be for the ARM target relative to that of the 8051 (bigger/smaller/indeterminate)?
Impossible to tell without knowing more about the actual code.
If the code is doing a lot of things that the 8051 is good at (bit manipulation, unsigned 8 bit arithmetics), then the equivalent for ARM is probably going to be larger.
If the code is doing a lot of things that the 8051 is not so good at (16/32/64 bit arithmetics, floating point math, pointers, dynamic memory allocation), then the equivalent ARM code may well be smaller.
"what would the expected size of program code be for the ARM target relative to that of the 8051 (bigger/smaller/indeterminate)?"
For Cortex I would say 25-40% bigger