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Variation in the current consumption due to memory address and offset value?

Hello to all,

 

I am trying to figure out the variation in current consumption as well as in clock cycles due to different memory regions and different offsets. During various experiments, I have found the following results:

 

LDR R4,[R1,#0x0]  (R1 = 0x00000000 (Flash) with 0 offset)  :   Current = 2.60mAmps & Cycles = 2

LDR R4,[R1,#0x1]  (R1 = 0x00000000 (Flash) with 1 offset)  :   Current = 2.07mAmps & Cycles = 4

LDR R4,[R1,#0x2]  (R1 = 0x00000000 (Flash) with 2 offset)  :   Current = 2.30mAmps & Cycles = 3

LDR R4,[R1,#0x3]  (R1 = 0x00000000 (Flash) with 3 offset)  :   Current = 2.08mAmps & Cycles = 4

 

from offset 4 it repeats the order. I mean Offset = 4 is equal to Offset = 0 ; Offset = 5 is equal to Offset = 1 ; Offset = 6 is equal to Offset = 2 ; Offset = 7 is equal to Offset = 3 ; Offset = 8 is equal to Offset = 0  and so on.... 

 

Similarly, while access SRAMX also :

 

LDR R4,[R1,#0x0]  (R1 = 0x04000000 (Flash) with 0 offset)  :   Current = 2.88mAmps & Cycles = 1

LDR R4,[R1,#0x1]  (R1 = 0x04000000 (Flash) with 1 offset)  :   Current = 2.30mAmps & Cycles = 3

LDR R4,[R1,#0x2]  (R1 = 0x04000000 (Flash) with 2 offset)  :   Current = 2.65mAmps & Cycles = 2

LDR R4,[R1,#0x3]  (R1 = 0x04000000 (Flash) with 3 offset)  :   Current = 2.29mAmps & Cycles = 3

 

from offset 4 it repeats the order. I mean Offset = 4 is equal to Offset = 0 ; Offset = 5 is equal to Offset = 1 ; Offset = 6 is equal to Offset = 2 ; Offset = 7 is equal to Offset = 3 ; Offset = 8 is equal to Offset = 0  and so on.... 

 

 

On the basis of observation, I have three questions:

  1. Why different offset value, results into different current consumption?
  2. Why offset value 4 shows the same result as offset 0 and so on?
  3. What is the reason for current variations, while accessing different memory regions?

 

Kindly help me out with this. I am using LPCXpresso 54114  board, with ARM Cortex-M4 processor. And all the measurement have been taken at 12MHz.

 

Thanking you,

 

Regards,

Himanshu