Maxim Integrated / OneWire

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Dependents:   MAXREFDES131_Qt_Demo MAX32630FTHR_iButton_uSD_Logger MAX32630FTHR_DS18B20_uSD_Logger MAXREFDES130_131_Demo ... more

OneWire_Masters/GPIO/owlink.s

Committer:
IanBenzMaxim
Date:
2016-03-29
Revision:
30:fdd7a0f82f2f
Parent:
29:5c51a17cfbf5
Child:
31:7c684e49fa8f

File content as of revision 30:fdd7a0f82f2f:

PROC_CLOCK_MHZ EQU 24 ; Processor clock in MHz
OVERHEAD_TUNING EQU 21 ; Fraction where OverheadTime(us) = OVERHEAD_TUNING / PROC_CLOCK_MHZ
; Make PROC_CLOCK_MHZ and OVERHEAD_TUNING divisible by PROC_CYCLES_PER_LOOP for best results

PIPELINE_REFILL_PROC_CYCLES EQU 1 ; ARM specifies 1-3 cycles for pipeline refill following a branch
PROC_CYCLES_PER_LOOP EQU (2 + PIPELINE_REFILL_PROC_CYCLES)
LOOPS_PER_US EQU (PROC_CLOCK_MHZ / PROC_CYCLES_PER_LOOP) ; Number of loop passes for a 1 us delay
LOOPS_REMOVED_TUNING EQU (OVERHEAD_TUNING / PROC_CYCLES_PER_LOOP)
 
#ifdef TOOLCHAIN_IAR 
  SECTION owlink : CODE
#else
  AREA owlink, CODE
#endif

; void ow_usdelay(unsigned int time_us)
  EXPORT ow_usdelay
ow_usdelay
  mov R1, #LOOPS_PER_US
  mul R0, R0, R1
  sub R0, R0, #LOOPS_REMOVED_TUNING
loop
  subs R0, R0, #1
  bne loop
  bx R14
  
  END