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I am using the following 3 assembly sections to read a memory mapped i/o to multiple registers and to read same i/o and save it ram respectively , on an ARM Cortex M3. I want to know exactly how many CPU cycles this would take to complete. Or in other words how fast am I reading the register.
1) read to and save to memory: Can LDR-STR=LDR-STR be tightly pipelined (With Address Phase of one instruction overlapping Data Phase of previous instruction), in which case the following will take only 9 cycles ?
486: 781a ldrb r2, [r3, #0]
488: 7002 strb r2, [r0, #0]
48a: 781a ldrb r2, [r3, #0]
48c: 7042 strb r2, [r0, #1]
48e: 781a ldrb r2, [r3, #0]
490: 7082 strb r2, [r0, #2]
492: 781a ldrb r2, [r3, #0]
494: 70c2 strb r2, [r0, #3]
2) read to multiple registers: I am assuming these instructions take 5 cycles.
48a: 781a ldrb r4, [r3, #0]
48e: 781a ldrb r5, [r3, #0]
492: 781a ldrb r6, [r3, #0]
I appreciate any insight you can provide.
Thanks,
As there are differences between various Cortex-M3 implementations, I'd like to ask you which microcontroller (vendor and chip name) you are using or plan on using ?
-If I'm lucky, I might have one, so I can make further tests (or someone reading this might be able to make a few tests).