\ msdelay.txt by Terry Porter May2016
\ STM32F0 Discovery Board (running from the internal 8MHz RC clock) program to :-
\ provide a timed delay in 1mS intervals using the systick and a timer
\ i.e " 1000 msdelay " which gives a 1 second delay
\ Flash the BLUE led every second by counting 1000 systicks
\ A 1mS marker is available on PB2


 \ Define Systick memory mapping as its not in CMSIS-SVD
 $E000E010 CONSTANT STK_CSR	\ SysTick control and status register. R/W reset value = $00000000
 $E000E014 CONSTANT STK_RVR	\ SysTick reload value register. R/W reset value = 6000 for the STM32F0
 $E000E018 CONSTANT STK_CVR	\ SysTick current value register. R/W value unknown  
 $E000E01C CONSTANT STK_CALIB	\ SysTick calibration value register. Read Only, $40001770 for the STM32F0
 0 variable second_counter
 0 variable ms_second_counter


 : INIT-SYSTICK
 %01  4 lshift GPIOB_MODER bis!     \ set PB2 to push pull output for the Marker
 %01 8 2* lshift GPIOC_MODER bis!   \ PC8 as output for F0 Disco LED
 8080 STK_RVR !			    \ systick calib for 1ms using internal 8mhz osc <--CHANGE the 8080 to suit your own MCU !!
 %101 STK_CSR bis!		    \ systick enable
 ;

: ENABLE-SYSTICK-INTERRUPT %010 STK_CSR bis! ;

: marker-set			    \ 1mS pulse for scope at PB2
 %1  2 lshift GPIOB_BSRR bis!       \ set PB2 = 1
 ;

 : marker-clear
 %1  18 lshift GPIOB_BSRR bis!      \ clear PB2
 ;

 : toggle-systick-led
    GPIOC_ODR @
    1 8 lshift xor
    GPIOC_ODR !
 ;

  

 INIT-SYSTICK

 : systick-handler
 ms_second_counter @
 1+
 ms_second_counter !
 marker-set
 second_counter @
 1+			    \ add one to the counter
 dup
 1000 >= if		    \ If counter is > = 1000 ...
 toggle-systick-led	    \ blink the LED at 1s rate
 drop			    \ drop the counter value of 1000  from the stack
 0			    \ put 0 on the stack to load in the counter after the 'then'
 then
 second_counter !	    \ reset the counter to zero
 marker-clear
 ;

 ' systick-handler irq-systick !
 ENABLE-SYSTICK-INTERRUPT



: msdelay cr
>R			    \ save delay value on the return stack
0 ms_second_counter !	    \ reset ms_second_counter to zero
BEGIN
R@			    \ copy the delay value
ms_second_counter @	    \ get ms_second_counter value
=			    \ loop until equal to  ms_second_counter
UNTIL
R> DROP			    \ balance the Return Stack
;			    \ finished, delay is over


\ ******* screenpic of a 1 minute delay *********
\ 60000 msdelay 
\ ok.