I am running a 10KHz interrupt running some mathmatical DSP code. It has to complete within 100 microseconds and preferably less than 40 microseconds to give me spare processing power. I decided to run the code on the simulator and using the Performance Analyzer Window on the software simulator it said the interrupt routine was taking 33 microseconds and as taking a third of the overall CPU power. Great I thought! However when I run the code for real I found it was taking abou 3 times as long and there is barely any spare processing power for my other routines. Any ideas? Some technical information: - I am using PK166 V5.03 - Both the simulator and target are running at 40MHz. - The code is a deterministic block of maths, i.e. there are no time outs or waiting for I/Os. - The interrupt routine has the highest priority, also I checked on single stepping the target that no other interrupts are active. - I extensive tested the speed of the target code using a oscillscope and a spare I/O. I found that no single piece of the code is taking longer. The whole code just seems to run slower than the simulator by about 2 - 3 times. - I know the target is running at 40MHz because all the PWM frequencies and CAN frequencies are as expected.
Hi, thanks for replying. Yes I should have said about that. I am using the XC164 in single chip mode. Yesterday I checked the number of wait states and found it was set at 4 waitstates. After consulting the keil website I found that for XC16X chips working above 32 MHz 2 waitstates are recommended. Great I thought - back to full speed! Once I did this I only got a 20% boost in speed so I'm still more than twice as slow as the Performance Analyser says I should be. (80 versus 33 microseconds). I've got all the options turned on for CPU branch prediction, instruction FIFOs set at 3 and all that stuff. Hmmm must be something obvious but I don't know what......
Hi I am not a DSP expert, but do you use the DSP library provided by Infineon ? There are handoptimized assembler routines, which uses DPRAM. ( Maybe you can take some inspiration from this ) And as if the problem is regarding the DSP part itself (speed), could the alternative be to execute this part from PSRAM ? Stefan
That is me again, I remember that the default reset values for the PLL where changed. E.g. the AC steps have maximum VCO base frequency / 16 and BA/BB steps have minimum VCO base frequency / 16. Did you check these settings? Stefan
Hi thanks for replying, Yes I am using the infineon dsp libary and alot of 32/16 bit integer divides using the inbuilt math routines. What upsets me is not so much how long its taking, it more that the simulator is producing a different timing answer to the reality. Maybe it doesn't properly include the time spent in the maths routines which are not inline but called from my 10KHz function. I have explictly set the pll. I am using a 8MHz crystal with PLL setting of: _PLLODIV EQU 3 ; 0 .. 14 Fpll = Fvco / (PLLODIV+1) ; 15 = reserved ; ; <o> PLLIDIV: PLL Input Divider (PLLCON.4 .. PLLCON.5) <0-3> ; Fin = Fosc / (PLLIDIV+1) _PLLIDIV EQU 0 ; 0 .. 3 Fin = Fosc / (PLLIDIV+1) ; ; <o> PLLVB: PLL VCO Band Select (PLLCON.6 .. PLLCON.7) ; <0=> Ouput:100-150MHz / Base:20-80MHz <1=> Ouput:150-200MHz / Base:40-130MHz ; <2=> Ouput:200-250MHz / Base:60-180MHz <3=> (250...300 MHz) Reserved _PLLVB EQU 1 ; ValueVCO output frequency Base frequency ; 0 = 100...150 MHz 20...80 MHz ; 1 = 150...200 MHz 40...130 MHz ; 2 = 200...250 MHz [def.] 60...180 MHz ; 3 = (250...300 MHz) Reserved ; ; <o> PLLMUL: PLL Multiplication Factor (PLLCON.8 .. PLLCON.12) <6-31> ; Fvco = Fin * (PLLMUL+1) _PLLMUL EQU 19 ; 7 .. 31 Fvco = Fin * (PLLMUL+1) ; 0 .. 6 = reserved ; ; <o> PLLCTRL: PLL Operation Control (PLLCON.13 .. PLLCON.14) ; <0=> Bypass PLL clock mult., the VCO is off <1=> Bypass PLL clock mult., the VCO is running ; <2=> VCO clock used, input clock switched off <3=> VCO clock used, input clock connected _PLLCTRL EQU 3 ; 0 = Bypass PLL clock mult., the VCO is off ; 1 = Bypass PLL clock mult., the VCO is running ; 2 = VCO clock used, input clock switched off ; 3 = VCO clock used, input clock connected I know the cpu clock is running at 40MHz because the UART and CAPCOM6 signals run off the same clock tree and produce the expected output frequencies. I assume other people have verified code timings produce by this simulator?