Trying to understand this snippet!

[Ian Rogers]

I know HOW it works but trying to change it into C is being problematic..

The 10 bit ADC result is thrown through a "rolling average" and it's result should be representative of a 12 bit answer!!

I just can't make it work in C

It is written for the H8 532 Processor FBB0 through FBDE are ram locations FBB0~FBBE are the 10 bit results BEFORE the average and are 12 bit after!!!

Can anyone identify this simple algorithm??

; averaging
;
AVERAGING:   MOV:G.B    #H'08:8,R4     ; 8 inputs
     MOV:G.W    #H'FBB0:16,R5     ; ADCresults : FBB0 ~ FBBE
     MOV:G.W    #H'FBD0:16,R6     ; Rolling Sum : FBD0 ~ FBDE
AVERAGING1:   MOV:G.W    @R6,R2
     MOV:G.W    @R6,R3       ; Get rolling sum
     SHLR.W     R3
     SHLR.W     R3
     SHLR.W     R3       ; Divide by 8
     SUB.W     R3,R2       ; Remove from rolling sum
     ADD:G.W    @R5,R2       ; Add ADC result
     MOV:G.W    R2,@R6       ; Store rolling sum
     SHLR.W     R2
     SHLR.W     R2
     SHLR.W     R2       ; Divide by 8
     MOV:G.W    R2,@R5       ; Averaged ADC result
     ADD:Q.W    #2,R5       ; Next ADC result
     ADD:Q.W    #2,R6       ; Next rolling sum
     ADD:Q.B    #-1,R4       ;
     BNE     AVERAGING1
     JMP     @H'22A8       ; Done..

 

[Ian Rogers]

Update.... I found a shift somewhere else in the code, so The input is also 12 bit!!

 

[Ian Rogers]

For anyone who took a look at this, I have missed a big part!!

The ADC was set up in scan mode ( I missed that ) each channel is rotated, byte swapped AND summed before the averaging routine..... It's going to take me a while longer to sort!!

Sorry for anyone who tried to make sense of this... If you are interested I'll post the answer some time soon..

 

[jpanhalt]

Ian, I am interested and did take more than a passing glance at it. Of course, I have no experience with Hitachi syntax; although, the comments helped. I think I see what it is doing from an algorithm standpoint, but I didn't want to make a fool of myself, so I will wait.

John