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Variation in current consumption for different offsets in memory regions why?

Question asked by HIMANSHU DOSHI on Sep 15, 2017
Latest reply on Sep 18, 2017 by jeremyzhou

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 = 1Offset = 6 is equal to Offset = 2Offset = 7 is equal to Offset = 3Offset = 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 two question:

  1. Why different offset value, results into different current consumption?
  2. 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

 

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