IO Stepper Linistep LINI_ASM_V21.ASM

; ******
<META http-equiv="Bulletin-Text" content="">


************************************************************************
;
;  LiniStepper v2
;  PIC 16F84 / 16F628 / 16F628A code (updated 628A June 2007)
;  Copyright Aug 2002 - Nov 2009 - Roman Black   http://www.romanblack.com
;
;  PIC assembler code for the LiniStepper stepper motor driver board.
;  200/400/1200/3600 steps
;
;  v2.0	New version 2.0; 2nd Nov 2009.
;		* modified v1 source to work with new Lini v2 PCB.
;		* STEP and DIR are the same, but POWER is now "ENABLE" (active LOW)
;		  (so the POWER pin function is inverted in Lini v2) 
;  v2.1   Updated 16th Nov 2010.
;		Now incorporates update suggested by Brian D Freeman; improves
;         performance by skipping the current calculation on the hi-lo
;         transition of the step input.
;
;  (set mplab TABS to 5 for best viewing this .asm file)
;******************************************************************************


;==============================================================================
; mplab settings

	ERRORLEVEL -224		; suppress annoying message because of option/tris
	ERRORLEVEL -302		; suppress message because of bank select in setup ports

	LIST b=5, n=97, t=ON, st=OFF		;
	; absolute listing tabs=5, lines=97, trim long lines=ON, symbol table=OFF

;==============================================================================
; processor defined

	;include <p16f84A.inc>
	;include <p16f628.inc>
	include <p16f628A.inc>

; processor config

	IFDEF __16F84A
		__CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_ON & _HS_OSC
	ENDIF
	IFDEF __16F628
		__CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_ON & _HS_OSC & _MCLRE_ON & _BODEN_OFF & _LVP_OFF
	ENDIF
	IFDEF __16F628A
		__CONFIG   _CP_OFF & _WDT_OFF & _PWRTE_ON & _HS_OSC & _MCLRE_ON & _BODEN_OFF & _LVP_OFF
	ENDIF


;==============================================================================
; Variables here

	;-------------------------------------------------
	IFDEF __16F84A
		#define RAM_START	0x0C
		#define RAM_END	RAM_START+d'68' 		; 16F84 has only 68 ram
	ENDIF
	IFDEF __16F628
		#define RAM_START	0x20	
		#define RAM_END	RAM_START+d'96' 		; F628 has 96 ram
	ENDIF
	IFDEF __16F628A
		#define RAM_START	0x20	
		#define RAM_END	RAM_START+d'96' 		; F628A has 96 ram
	ENDIF
	;-------------------------------------------------
	CBLOCK 	RAM_START

		status_temp		; used for int servicing
		w_temp			; used for int servicing

		step				; (0-71) ustep position!
		steptemp			; for calcs

		phase			; stores the 4 motor phase pins 0000xxxx
		current1			; for current tween pwm
		current2			; for current tween pwm

		inputs			; stores new input pins
		inputs_last		; stores last states of input pins

	ENDC

	;-------------------------------------------------
	; PIC input pins for porta

	#define 	STEP			0		; / = move 1 step, \=do nothing
	#define 	DIR			1		; lo= cw,  hi=ccw
	#define 	POWER		2		; lo=full power, hi=half power
			; (Note! POWER pin was inverted for v2 !!!)
	;-------------------------------------------------
	; Custom instructions!

	#define	skpwne		skpnz			; after subxx, uses zero
	#define	skpweq		skpz				; after subxx, uses zero
	#define	skpwle		skpc				; after subxx, uses carry
	#define	skpwgt		skpnc			; after subxx, uses carry

;==============================================================================
; CODE GOES HERE

	org 0x0000 			; Set program memory base at reset vector 0x00
reset
	goto main				;



;==============================================================================
; INTERRUPT vector here
	org 0x0004 			; interrupt routine must start here
int_routine

	;-------------------------------------------------
						; first we preserve w and status register

	movwf w_temp      		; save off current W register contents
	movf	STATUS,w          	; move status register into W register
	movwf status_temp       	; save off contents of STATUS register
	;-------------------------------------------------
						; we get here every 256 timer0 ticks  3900Hz
						; int body code here if you want

	;-------------------------------------------------
						; finally we restore w and status registers and
						; clear TMRO int flag now we are finished.
int_exit
	bcf INTCON,T0IF		; reset the tmr0 interrupt flag
	movf status_temp,w     	; retrieve copy of STATUS register
	movwf STATUS            	; restore pre-isr STATUS register contents
	swapf w_temp,f
	swapf w_temp,w          	; restore pre-isr W register contents
	retfie				; return from interrupt
	;-------------------------------------------------

;==============================================================================




;******************************************************************************
; MOVE MOTOR  		  sets 8 portb output pins to control motor
;******************************************************************************
; NOTE!! var step is used for sequencing the 0-71 steps
; uses tables! so keep it first in the code and set PCLATH to page 0

;------------------
move_motor				; goto label
;------------------

	;-------------------------------------------------
	; this code controls the phase sequencing and current
	; settings for the motor.

	; there are always 72 steps (0-71)

	; we can split the main table into 2 halves, each have identical
	; current sequencing. That is only 12 entries for hardware current.

	; Then can x3 the table to get 36 table entries which cover all 72 steps.
	; the 36 entries jump to 36 code pieces, which set the current values
	; for the 2 possible tween steps... We need 2 current values, one
	; for the x2 value and one for the x1 value.
	;-------------------------------------------------
	; PHASE SEQUENCING (switch the 4 coils)

	; there are 4 possible combinations for the phase switching:
	; each have 18 steps, total 72 steps:

	;	A+ B+	range 0		step 0-17
	;	A- B+	range 1		18-35
	;	A- B-	range 2		36-53
	;	A+ B-	range 3		54-71

	;-------------------------------------------------
						; find which of the 4 ranges we are in
	movf step,w			; get step
	movwf steptemp			; store as working temp

	movf steptemp,w		;
	sublw d'35'			; sub to test
	skpwle				;
	goto half_hi			; wgt, steptemp is 36-71 (upper half)

	;-------------------------
half_low					; wle, steptemp is 0-35

	movf steptemp,w		;
	sublw d'17'			; sub to test
	skpwle				;
	goto range1			; wgt
	
range0					; wle
	movlw b'00000101'		; 0101 = A+ B+
	goto phase_done		;

range1
	movlw b'00001001'		; 1001 = A- B+
	goto phase_done		;

	;-------------------------
half_hi					; steptemp is 36-71
						; NOTE! must subtract 36 from steptemp, so it
						; will become 0-35 and ok with table later!
	movlw d'36'			; subtract 36 from steptemp,
	subwf steptemp,f		; (now steptemp is 0-35)

						; now find the range
	movf steptemp,w		;
	sublw d'17'			; sub to test
	skpwle				;
	goto range3			; wgt
	
range2					; wle
	movlw b'00001010'		; 1010 = A- B-
	goto phase_done		;

range3
	movlw b'00000110'		; 0110 = A+ B-

phase_done				; note! steptemp is always 0-35 by here
	movwf phase			; store phase values

	;-------------------------------------------------
	; at this point we have the phasing done and stored as the last
	; 4 bits in var phase; 0000xxxx
	
	; now we have 36 possible current combinations, which we can do
	; by separate code fragments, from a jump table.

	; as we have 2 power modes; full and low power, we
	; need 2 tables.

	;-------------------------------------------------

	btfsc inputs,POWER		; select table to use
	goto table_lowpower		;

	;-------------------------------------------------
	; HIGH POWER TABLE
	;-------------------------------------------------

table_highpower			;

	movf steptemp,w		; add steptemp to the PCL
	addwf PCL,f			; 
						; here are the 36 possible values;
	;-------------------------
	goto st00				; * (hardware 6th steps)
	goto st01				;   (pwm tween steps)
	goto st02				;   (pwm tween steps)
	goto st03				; *
	goto st04				; 
	goto st05				; 

	goto st06				; *
	goto st07				;
	goto st08				;
	goto st09				; *
	goto st10				;
	goto st11				;

	goto st12				; *
	goto st13				;
	goto st14				;
	goto st15				; *
	goto st16				;
	goto st17				;

	goto st18				; *
	goto st19				;
	goto st20				;
	goto st21				; *
	goto st22				;
	goto st23				;

	goto st24				; *
	goto st25				;
	goto st26				;
	goto st27				; *
	goto st28				;
	goto st29				;

	goto st30				; *
	goto st31				;
	goto st32				;
	goto st33				; *
	goto st34				;
	goto st35				;

	;-------------------------------------------------
	; LOW POWER TABLE
	;-------------------------------------------------
	; as low power mode is for wait periods we don't need to
	; maintain the full step precision and can wait on the
	; half-step (400 steps/rev). This means much easier code tables.
	; The nature of the board electronics is not really suited
	; for LOW power microstepping, but it could be programmed here
	; if needed.

	; NOTE!! uses my hi-torque half stepping, not normal half step.

	;  doing half stepping with the 55,25 current values gives;
	; 55+25 = 80
	; max current 100+100 = 200
	; typical (high) current 100+50 = 150
	; so low power is about 1/2 the current of high power mode,
	; giving about 1/4 the motor heating and half the driver heating.

	; for now it uses only half-steps or 8 separate current modes.
	; we only have to use 4 actual current modes as
	; the table is doubled like the table_highpower is.

	; NOTE!! I have left the table full sized so it can be modified
	; to 1200 or 3600 steps if needed.
	;-------------------------------------------------

table_lowpower				;

	movf steptemp,w		; add steptemp to the PCL
	addwf PCL,f			; 
						; here are the 36 possible values;
	;-------------------------
						; A+ B+ (A- B-)

	goto lp00				;
	goto lp00				;
	goto lp00				;
	goto lp00				;
	goto lp00				;	55,25 (100,45) current low (high)
	goto lp00				;
	goto lp00				;
	goto lp00				;
	goto lp00				;

	goto lp09				;
	goto lp09				;
	goto lp09				;
	goto lp09				;
	goto lp09				;	25,55 (45,100)
	goto lp09				;
	goto lp09				;
	goto lp09				;
	goto lp09				;

	;-------------------------
						; A- B+ (A+ B-)

	goto lp18				;
	goto lp18				;
	goto lp18				;
	goto lp18				;
	goto lp18				;	25,55 (45,100)
	goto lp18				;
	goto lp18				;
	goto lp18				;
	goto lp18				;

	goto lp27				;
	goto lp27				;
	goto lp27				;
	goto lp27				;
	goto lp27				;	55,25 (100,45)
	goto lp27				;
	goto lp27				;
	goto lp27				;
	goto lp27				;

	;-------------------------------------------------
	; all tables done, no more tables after this point!
	;-------------------------------------------------
	; next are the 36 code fragments for the high power table.

	; CURRENT INFO.
	; hardware requires that we send the entire 8 bits to the motor
	; at one time, to keep pwm fast.

	; ----xxxx,  where xxxx is the coils on/off phasing (done)
	; xxxx----,  where xxxx is the current settings for the A and B phases;
	; xx------,  where xx is current for A phase
	; --xx----,  where xx is current for B phase

	; hardware currents for 6th stepping have 4 possible values;
	; 00  =  0% current
	; 01  =  25% current
	; 10  =  55% current
	; 11  =  100% current

	;-------------------------------------------------
	; PWM INFO.
	; hardware gives us 6th steps, or 1200 steps/rev.
	; to get 3600 steps/rev we need TWO more
	; "tween" steps between every proper hardware 6th step.

	; to do this we set 2 currents, current1 and current2.
	; then we do FAST pwm, with 2 time units at current2,
	; and 1 time unit at current1.
	; this gives a current which is between the two currents,
	; proportionally closer to current2. (2/3 obviously)
	; this gives the ability to get 2 evenly spaced "tween" currents
	; between our hardware 6th step currents, and go from 1200 to 3600.

	; the next 36 code fragments set the 2 currents desired, then
	; we goto a fast-pwm loop (same loop used for all currents)
	; which modulates between the 2 currents and gives final
	; output current.
	;-------------------------------------------------

st00						; (6th step)
	movf phase,w			; get coil phasing (is 0000xxxx)
	iorlw b'11000000'		; set currents; 100,0 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st01						; (tween step)
	movf phase,w			; get coil phasing
	iorlw b'11000000'		; set 100,0 
	movwf current2			;
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current1			;
	goto pwm				;

st02						; (tween step)
	movf phase,w			; get coil phasing
	iorlw b'11010000'		; set 100,25 
	movwf current2			;
	movf phase,w			;
	iorlw b'11000000'		; set 100,0 
	movwf current1			;
	goto pwm				;

	;-------------------------

st03						; (6th step)
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st04						;
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current2			;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current1			;
	goto pwm				;

st05						;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current2			;
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current1			;
	goto pwm				;

	;-------------------------

st06						; (6th step)
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st07						;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current2			;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current1			;
	goto pwm				;

st08						;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100
	movwf current2			;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current1			;
	goto pwm				;

	;-------------------------

st09						; (6th step)
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st10						;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current2			;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current1			;
	goto pwm				;

st11						;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100
	movwf current2			;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current1			;
	goto pwm				;

	;-------------------------

st12						; (6th step)
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st13						;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current2			;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current1			;
	goto pwm				;

st14						;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100
	movwf current2			;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current1			;
	goto pwm				;

	;-------------------------
st15						; (6th step)
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st16						;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current2			;
	movf phase,w			;
	iorlw b'00110000'		; set 0,100 
	movwf current1			;
	goto pwm				;

st17						;
	movf phase,w			;
	iorlw b'00110000'		; set 0,100
	movwf current2			;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current1			;
	goto pwm				;

	;-------------------------
	;-------------------------

st18						; (6th step)
	movf phase,w			;
	iorlw b'00110000'		; set 0,100 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st19						;
	movf phase,w			;
	iorlw b'00110000'		; set 0,100 
	movwf current2			;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current1			;
	goto pwm				;

st20						;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100
	movwf current2			;
	movf phase,w			;
	iorlw b'00110000'		; set 0,100 
	movwf current1			;
	goto pwm				;

	;-------------------------

st21						; (6th step)
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st22						;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current2			;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current1			;
	goto pwm				;

st23						;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100
	movwf current2			;
	movf phase,w			;
	iorlw b'01110000'		; set 25,100 
	movwf current1			;
	goto pwm				;

	;-------------------------

st24						; (6th step)
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st25						;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current2			;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current1			;
	goto pwm				;

st26						;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100
	movwf current2			;
	movf phase,w			;
	iorlw b'10110000'		; set 55,100 
	movwf current1			;
	goto pwm				;

	;-------------------------

st27						; (6th step)
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st28						;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current2			;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current1			;
	goto pwm				;

st29						;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55
	movwf current2			;
	movf phase,w			;
	iorlw b'11110000'		; set 100,100 
	movwf current1			;
	goto pwm				;

	;-------------------------

st30						; (6th step)
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st31						;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current2			;
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current1			;
	goto pwm				;

st32						;
	movf phase,w			;
	iorlw b'11010000'		; set 100,25
	movwf current2			;
	movf phase,w			;
	iorlw b'11100000'		; set 100,55 
	movwf current1			;
	goto pwm				;

	;-------------------------

st33						; (6th step)
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current2			;
	movwf current1			;
	goto pwm				;

st34						;
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current2			;
	movf phase,w			;
	iorlw b'11000000'		; set 100,0 
	movwf current1			;
	goto pwm				;

st35						;
	movf phase,w			;
	iorlw b'11000000'		; set 100,0
	movwf current2			;
	movf phase,w			;
	iorlw b'11010000'		; set 100,25 
	movwf current1			;
	goto pwm				;
						; high power table done!


	;-------------------------------------------------
	; next are the 4 code fragments for the low power table.
	; (no PWM is used)
	;-------------------------------------------------

lp00						;
	movf phase,w			;
	iorlw b'10010000'		; set 55,25 
	movwf current2			;
	movwf current1			;
	goto pwm				;

lp09						;
	movf phase,w			;
	iorlw b'01100000'		; set 25,55 
	movwf current2			;
	movwf current1			;
	goto pwm				;

lp18						;
	movf phase,w			;
	iorlw b'01100000'		; set 25,55 
	movwf current2			;
	movwf current1			;
	goto pwm				;

lp27						;
	movf phase,w			;
	iorlw b'10010000'		; set 55,25
	movwf current2			;
	movwf current1			;
	goto pwm				;

	;-------------------------------------------------


;------------------------------------------------------------------------------




;******************************************************************************
;  Main 
;******************************************************************************
;
;------------------
main						; goto label
;------------------

	;---------------------------------------------
						; do initial setup for ports and ints and stuff
	call setup			; this is our only proper call...
						; it is called only once, and does not really need
						; to be a function.
	;---------------------------------------------
	; main operating loop is here.
	;---------------------------------------------

	goto move_motor		; will set the motor to step 0,
						; and loop permanently from there

	;---------------------------------------------
	goto main				; safe loop, should never get here anyway.

;==============================================================================




;******************************************************************************
; NEW INPUTS   input change was detected
;******************************************************************************
;
;------------------
new_inputs				; goto tag
;------------------

	;-------------------------------------------------
	; when we enter here:
	; * one or more PORTA inputs have just changed
	; * inputs_last	contains last PORTA inputs values
	; * inputs		contains new PORTA inputs values
	;-------------------------------------------------
	; must first detect which input pins changed.

	; ---x----	RA4	* mode bit1	   ( 00=200 step	01=400 step
	; ----x---	RA3	* mode bit0		10=1200 step	11=3600 step )
	; -----x--	RA2	* power  (Lini v2; now 0 = full power!)
	; ------x-	RA1	* direction
	; -------x	RA0	* step

	; if step went hi, we move the step (step++ or step--)

	; if step went low, ignore
	; ignore change in direction pin
	; ignore change in power pin
	; ignore change in mode pins
	; (all pins besides step are handled automatically in move_motor)
	;-------------------------------------------------

	movf inputs,w			; xor to compare new inputs with last values
	xorwf inputs_last,f		; now inputs_last has the diff.

	btfss inputs_last,STEP	; test if step input changed
	goto ni_end			; 

						; step input changed!
	btfsc inputs,STEP		; test if change was lo-hi or hi-lo
	goto trans_hi			; lo-hi, so process a step!

						; hi-lo, so ignore this transition
	bcf inputs_last,STEP	; record new state of step pin
	goto pwm				; fast exit back to pwm()

	;-------------------------------------------------
	; step input changed lo-hi!
	; now must make a step forward or back, based
	; on the state of the dir pin.

	; here it gets complex as we have 4 operating modes,
	; determined by the state of the 2 input pins RA4 and RA3;

	; ---00---	200 steps
	; ---01---	400 steps
	; ---10---	1200 steps
	; ---11---	3600 steps

	; there are 4 separate code systems to handle stepping 
	; in the 4 modes;
	;-------------------------------------------------
trans_hi
						; find which of the 4 modes we are in
	btfss inputs,4			; test hi bit
	goto mode_lo			;

mode_hi					; must be 1200 or 3600

	btfss inputs,3			; test lo bit
	goto mode_1200			;

	;-------------------------------------------------
mode_3600					; 3600 mode (72/1)
						; each step is 1

	btfss inputs,DIR		; test direction input
	goto m36_up			;

m36_down
	decf step,f			; step--
	btfss step,7			; test for roll under <0
	goto ni_end			; ok
						; rolled under!
	movlw d'71'			; force to top step (72-1)
	movwf step			;
	goto ni_end			;

m36_up
	incf step,f			; step++
	movf step,w			; test for roll over >71
	sublw d'71'			; sub to test
	skpwle				;
	clrf step				; wgt, rolled over so force to step 0

	goto ni_end			;
	;-------------------------------------------------
mode_1200					; 1200 mode (72/3)
						; each step is mod 3 (0,3,6,9,12 - 66, 69 etc)

	btfss inputs,DIR		; test direction input
	goto m12_up			;

m12_down
	movlw d'3'			; amount to subtract
	subwf step,f			; step-=3
	btfss step,7			; test for roll under <0
	goto ni_end			; ok
						; rolled under!
	movlw d'69'			; force to top step (72-3)
	movwf step			;
	goto ni_end			;

m12_up
	movlw d'3'			; amount to add
	addwf step,f			; step+=3
						;
	movf step,w			; test for roll over >69
	sublw d'69'			; sub to test
	skpwle				;
	clrf step				; wgt, rolled over so force to step 0

	goto ni_end			;
	;-------------------------------------------------
mode_lo					; must be 200 or 400
	btfss inputs,3			; test lo bit
	goto mode_200			;

	;-------------------------------------------------
mode_400					; 400 mode (72/9)
						; note! we do special half stepping here.
						; there are ONLY 8 valid steps:
						; 4, 13, 22, 31, 40, 49, 58, 67
						; these steps give 100,45 and 35,100 combos, good
						; enough for now. (should average 100,41)

	btfss inputs,DIR		; test direction input
	goto m4_up			;

m4_down
	movlw d'9'			; amount to subtract
	subwf step,f			; step-=9
	btfss step,7			; test for roll under <0
	goto ni_end			; ok
						; rolled under!
	movlw d'67'			; force to top (full) step 
	movwf step			;
	goto ni_end			;

m4_up
	movlw d'9'			; amount to add
	addwf step,f			; step+=9
						;
	movf step,w			; test for roll over
	sublw d'67'			; sub to test
	skpwgt				;
	goto ni_end			; wle, is ok

	movlw d'4'			; wgt, rolled over so force to bottom step 5
	movwf step			;

	goto ni_end			;
	;-------------------------------------------------
mode_200					; 200 mode (72/18)
						; NOTE!! this has special needs as we can't use
						; step 0, we need to stay on the "2 steps on" steps.
						; there are ONLY 4 valid steps;  9, 27, 45, 63

	btfss inputs,DIR		; test direction input
	goto m2_up			;

m2_down
	movlw d'18'			; amount to subtract
	subwf step,f			; step-=18
	btfss step,7			; test for roll under <0
	goto ni_end			; ok
						; rolled under!
	movlw d'63'			; force to top (full) step (72-(18/2))
	movwf step			;
	goto ni_end			;

m2_up
	movlw d'18'			; amount to add
	addwf step,f			; step+=18
						;
	movf step,w			; test for roll over
	sublw d'63'			; sub to test
	skpwgt				;
	goto ni_end			; wle, is ok

	movlw d'9'			; wgt, rolled over so force to bottom step 9
	movwf step			;

	goto ni_end			;

	;-------------------------------------------------
ni_end
	movf inputs,w			; save a copy of the inputs
	movwf inputs_last		;

	goto move_motor		; go and make it all happen

;------------------------------------------------------------------------------




;******************************************************************************
; PWM		is the fast pwm loop
;******************************************************************************
; NOTE!! we enter the code in the middle of the loop!

	;-------------------------------------------------
	; the 2 target currents were set in the move_motor code.

	; what this function does is spend 2 time units at current2,
	; and 1 time unit at current1.
	; actual is 8 clocks at current2
	; and 4 clocks at current 1
	; total 12 cycles, so 333 kHz with 16MHz resonator.

	; this gives an average pwm current of 2/3 the way between
	; current2 and current1.

	; the routine is kept short to keep pwm frequency high, so it
	; is easy to smooth in hardware by the ramping caps.

	; IMPORTANT! is timed by clock cycles, don't change this code!
	; it also checks for any change in input pins here

	; the 8/4 code seen here was supplied by Eric Bohlman (thanks!)
	;-------------------------------------------------
pwm_loop
						; first output current1 to motor
	movf current1,w		; get currents and phase switching
	movwf PORTB			; send to motor!

	nop					; timing delay
	nop					;
						; (4 cycles)
	;-------------------------
pwm						; main entry!
						; better to enter at current2 for motor power.

						; now output current2
	movf current2,w		;
	movwf PORTB			; send to motor!
	nop					; safe wait 250nS

						; now test input pins
	movf PORTA,w			; get pin values from port

	xorwf inputs_last,w		; xor to compare new inputs with last values
	skpnz
	goto pwm_loop			; z, inputs not changed, so keep looping
						; (8 cycles)
	;-------------------------------------------------
						; nz, one or more input pins have changed!
	xorwf inputs_last,w		; restore xored value back to the orig inputs value
	movwf inputs			;

	goto new_inputs		; 
	;-------------------------------------------------

;------------------------------------------------------------------------------






;******************************************************************************
;  SETUP   sets port directions and interrupt stuff etc,
;******************************************************************************
; NOTE!! is the only proper funtion, is done before other activity

;------------------
setup					; routine tag
;------------------

	;-------------------------------------------------
	; Note! there are added bits for the 16F628!
	; here we set up peripherals and port directions.
	; this will need to be changed for different PICs.
	;-------------------------------------------------
						; OPTION setup
	movlw b'10000010'		;
		;  x-------		; 7, 0=enable, 1=disable, portb pullups
		;  -x------		; 6, 1=/, int edge select bit
		;  --x-----		; 5, timer0 source, 0=internal clock, 1=ext pin.
		;  ---x----		; 4, timer0 ext edge, 1=\
		;  ----x---		; 3, prescaler assign, 1=wdt, 0=timer0
		;  -----x--		; 2,1,0, timer0 prescaler rate select
		;  ------x-		;   000=2, 001=4, 010=8, 011=16, etc.
		;  -------x		; 
						;
	banksel OPTION_REG		; go proper reg bank
	movwf OPTION_REG		; load data into OPTION_REG
	banksel 0				;
	;-------------------------------------------------
	; note! check for 16F628 (and A) and do extra setup for it.

	IFDEF  __16F628
		banksel VRCON		; do bank 1 stuff
		clrf VRCON		; disable Vref
		clrf PIE1			; disable pi etc
		banksel 0			;

		clrf T1CON		; disable timer1
		clrf T2CON		; disable timer2
		clrf CCP1CON		; disable CCP module

		movlw b'00000111'	; disable comparators
		movwf CMCON		;
	ENDIF
	IFDEF  __16F628A
		banksel VRCON		; do bank 1 stuff
		clrf VRCON		; disable Vref
		clrf PIE1			; disable pi etc
		banksel 0			;

		clrf T1CON		; disable timer1
		clrf T2CON		; disable timer2
		clrf CCP1CON		; disable CCP module

		movlw b'00000111'	; disable comparators
		movwf CMCON		;
	ENDIF
	;-------------------------------------------------
						; PORTB pins direction setup
						; 1=input, 0=output
	clrf PORTB			;
						;
	movlw b'00000000'		; all 8 portb are outputs
						;
	banksel TRISB			; go proper reg bank
	movwf TRISB			; send mask to portb
	banksel 0				;
	;-------------------------------------------------

						; PORTA pins direction setup
						; 1=input, 0=output
	clrf PORTA			;

						; NOTE!! all 5 PORTA pins are inputs
	movlw b'00011111'		;
		;  ---x----		; RA4
		;  ----x---		; RA3
		;  -----x--		; RA2
		;  ------x-		; RA1
		;  -------x		; RA0

	banksel TRISA			; go proper reg bank
	movwf TRISA			; send mask to porta
	banksel 0				;
	;-------------------------------------------------

	movlw 0x00			; set up PCLATH for all jump tables on page 0
	movwf PCLATH			; (all tables are in move_motor)
	;-------------------------------------------------

						; CLEAR RAM! for lower bank
	movlw RAM_START		; first byte of ram
	movwf FSR				; load pointer
ram_clear_loop
	clrf INDF				; clear the ram we pointed to
	incf FSR,f			; inc pointer to next ram byte
	movf FSR,w			; get copy of pointer to w
	sublw RAM_END			; test if PAST the last byte now
	skpweq				;
	goto ram_clear_loop		;

	;-------------------------------------------------
						; here we can set the user variables and output pins

	movlw 0x00			; for step 0 of 0-71
	movwf step			; loaded ready for jump table

	movf PORTA,w			; get initial value for inputs
	movwf inputs			;
	movwf inputs_last		;

	;-------------------------------------------------
						; set up INTCON register last
	movlw b'00000000'		; set the bit value 

		;  x-------		; bit7 	GIE global int enable, 1=enabled
		;  -x------		; bit6	EE write complete enable, 1=en
		;  --x-----		; bit5 	TMR0 overflow int enable, 1=en
		;  ---x----		; bit4 	RB0/INT enable, 1=en
		;  ----x---		; bit3	RB port change int enable, 1=en
		;  -----x--		; bit2	TMR0 int flag bit, 1=did overflow and get int
		;  ------x-		; bit1	RB0/INT flag bit, 1=did get int
		;  -------x		; bit0	RB port int flag bit, 1=did get int

	movwf INTCON			; put in INTCON register
	;-------------------------------------------------
	return				;
;------------------------------------------------------------------------------





;==============================================================================
	; this code is only to display 1k of the memory usage chart
	; in the absolute listing!

	; page 0 256 byte block--------------------
	;org 0x40-2
	;nop
	;org 0x80-1
	;nop
	;org 0xC0-1
	;nop
	;org 0x100-1
	;nop

	; page 1 256 byte block--------------------
	;org 0x140-2
	;nop
	;org 0x180-1
	;nop
	;org 0x1C0-1
	;nop
	;org 0x200-1
	;nop

	; page 2 256 byte block--------------------
	org 0x240-2
	nop
	org 0x280-1
	nop
	org 0x2C0-1
	nop
	org 0x300-1
	nop

	; page 3 256 byte block--------------------
	org 0x340-2
	nop
	org 0x380-1
	nop
	org 0x3C0-1
	nop
	org 0x400-1
	nop


	IFDEF __16F628A
		; page 4 256 byte block--------------------
		org 0x440-2
		nop
		org 0x480-1
		nop
		org 0x4C0-1
		nop
		org 0x500-1
		nop

		; page 5 256 byte block--------------------
		org 0x540-2
		nop
		org 0x580-1
		nop
		org 0x5C0-1
		nop
		org 0x600-1
		nop

		; page 6 256 byte block--------------------
		org 0x640-2
		nop
		org 0x680-1
		nop
		org 0x6C0-1
		nop
		org 0x700-1
		nop

		; page 7 256 byte block--------------------
		org 0x740-2
		nop
		org 0x780-1
		nop
		org 0x7C0-1
		nop
		org 0x800-1
		nop
	ENDIF

	;-------------------------------------------------------------------------
	end
	;-------------------------------------------------------------------------

;==============================================================================
;==============================================================================
;==============================================================================



	;-------------------------------------------------
	; NOTE!! example! below is the original (non-pwm) table for the
	; 24x hardware 6th steps.
	; this will be useful to code a minimum-rom microstepper
	; if you don't need 3600 and can make do with 1200 steps.

	; same system as the main code;
	; ----xxxx	are the phase sequencing
	; xxxx----	are the current values

	; (this code table has been used and tested!)
	;-------------------------------------------------
	; COMMENTED OUT!

		;movlw b'11000101'		; 0,		100,0 	A+ B+	00=0		01=25
		;movlw b'11010101'		; 1,		100,25	A+ B+	10=55	11=100
		;movlw b'11100101'		; 2, 	100,55 	A+ B+
		;movlw b'11110101'		; 3, 	100,100	A+ B+
		;movlw b'10110101'		; 4, 	55,100	A+ B+
		;movlw b'01110101'		; 5, 	25,100	A+ B+
	;-------------------------
		;movlw b'00111001'		; 6, 	0,100	A- B+
		;movlw b'01111001'		; 7, 	25,100	A- B+
		;movlw b'10111001'		; 8, 	55,100	A- B+
		;movlw b'11111001'		; 9, 	100,100	A- B+
		;movlw b'11101001'		; 10, 	100,55	A- B+
		;movlw b'11011001'		; 11, 	100,25	A- B+
	;-------------------------
		;movlw b'11001010'		; 12, 	100,0	A- B-
		;movlw b'11011010'		; 13, 	100,25	A- B-
		;movlw b'11101010'		; 14, 	100,55	A- B-
		;movlw b'11111010'		; 15, 	100,100	A- B-
		;movlw b'10111010'		; 16, 	55,100	A- B-
		;movlw b'01111010'		; 17, 	25,100	A- B-
	;-------------------------
		;movlw b'00110110'		; 18, 	0,100	A+ B-
		;movlw b'01110110'		; 19, 	25,100	A+ B-
		;movlw b'10110110'		; 20, 	55,100	A+ B-
		;movlw b'11110110'		; 21, 	100,100	A+ B-
		;movlw b'11100110'		; 22, 	100,55	A+ B-
		;movlw b'11010110'		; 23, 	100,25	A+ B-



	EXAMPLE! full table example here, 0-71 steps showing every step...

	;-------------------------
	0	100,0 	A+ B+
	1	 100,8   (pwm tween)
	2	 100,17  (pwm tween)
	3	100,25	A+ B+
	4	 100,35  (pwm tween)
	5	 100,45  (pwm tween)
	6	100,55 	A+ B+
	7	 100,70  (pwm tween)	
	8	 100,85  (pwm tween)
	9	100,100	A+ B+	(rest of table is same, tweens not shown)
	10
	11
	12	55,100	A+ B+
	13
	14
	15	25,100	A+ B+
	16
	17
	;-------------------------
	18	0,100	A- B+
	19
	20
	21	25,100	A- B+
	22
	23
	24	55,100	A- B+
	25
	26
	27	100,100	A- B+
	28
	29
	30	100,55	A- B+
	31
	32
	33	100,25	A- B+
	34
	35
	;-------------------------
	36	100,0	A- B-
	37
	38
	39	100,25	A- B-
	40
	41
	42	100,55	A- B-
	43
	44
	45	100,100	A- B-
	46
	47
	48	55,100	A- B-
	49
	50
	51	25,100	A- B-
	52
	53
	;-------------------------
	54	0,100	A+ B-
	55
	56
	57	25,100	A+ B-
	58
	59
	60	55,100	A+ B-
	61
	62
	63	100,100	A+ B-
	64
	65
	66	100,55	A+ B-
	67
	68
	69	100,25	A+ B-
	70
	71
	;-------------------------------------------------
	

  .