IO Stepper Linistep Liniclock LINICLOCK_6HOUR.ASM

; ******************************************************************************
;
;  LiniClock_6hour.asm (one-hand analogue clock using LiniStepper V1 or v2 PCB)
;  PIC 16F628A code 
;  Copyright Sep 2010 - Roman Black   http://www.RomanBlack.com
;
;  200/400/1200/3600 steps
;  Clock uses one stepper motor to turn one hand. The clock takes exactly
;  6 hours for a full rotation, giving an attractive 6hour clock face
;  with a single "hours" hand.
;  The clock is driven directly from the PIC's 16MHz xtal OR
;  can be driven from 60Hz or 50Hz mains freq for high accuracy.
;  One button is used to "set" the clock by advancing the hand,
;  the clock set button is on pin RA0 and HI = clock set (Note!!
;  if using Lini v1 PCB you also need a 10k pull-down resistor on that
;  pin but on Lini v2 PCB the resistor is not needed).
;
;  This code was adapted from the Linistepper v2 code, the main difference
;  is that instead of advancing the motor 1 microstep when the step
;  input goes /, it now advances the motor one microstep every 25 seconds,
;  this gives exactly 6 hours per rotation with a cheap 48step/rev stepper
;  motor. (If using a 200step/rev motor, it will advance one microstep
;  every 6 seconds). Code was fully tested in hardware.
;
;  Dip switch J1 selects motor type; ON = 200step/rev motor, OFF = 48step/rev motor
;  Dip switch J2 selects clock source; ON = mains freq detect, OFF = PIC 16Mhz xtal
;
;  PORTA.F0 = clock set button; Hi = clock set
;  PORTA.F1 = 60Hz mains freq input (optional)
;  PORTA.F2 = 50Hz mains freq input (optional)
;  (note!! replace C5 and C6 with large caps >=22uF for good clock hand smoothing)
;
;  (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

		bres_hi			; hi byte of 24bit variable (for 1second timing)
		bres_mid			; mid byte
		bres_lo			; lo byte
		second_count		;
		input_edge		;
		hz_count			;

		button_debounce	; used for "clock set" button

	ENDC

	;-------------------------------------------------
	; NEW!! Just for LiniClock; set the stepper motor type!

	;#define   MOTOR_SECONDS	6	; This setting for 200step/rev motors
	#define   MOTOR_SECONDS	25	; This setting for 48step/rev motors

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

	#define 	CLOCK_SET		0		; HI = clock set
	#define 	Hz_60		1		; mains freq input
	#define 	Hz_50		2		; mains freq input (alternative)
	#define 	J1			3		; ON = HI = 200step/rev motor
	#define 	J2			4		; ON = HI = use mains freq input

	;-------------------------------------------------
	; 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 (int not used!)
	org 0x0004 			; interrupt routine must start here
int_routine

	;-------------------------------------------------
						; first we preserve w and status register
	movwf w_temp      		; 
	movf	STATUS,w          	; 
	movwf status_temp       	; 
	;-------------------------------------------------
						; we get here every TMR0 overflow 
						; 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		; must clear the overflow flag! 
	movf status_temp,w     	; 
	movwf STATUS            	; 
	swapf w_temp,f
	swapf w_temp,w          	; 
	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.

	;-------------------------------------------------
	; LiniClock note!! motor is always set to high power;
	;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.

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




;******************************************************************************
; UPDATE CLOCK     test if it is time to move the clock hand yet!
;******************************************************************************
;
;------------------
update_clock				; goto tag
;------------------

	;-------------------------------------------------
	; we enter here when TMR0 has overflowed (3906 Hz)
	; xtal is 16 MHz, TMR0 is 1:4 prescale so each TMR0
	; "tick" is 1uS (1 million ticks a second)
	; no interrupt is used, instead we poll for TMR0 overflow flag.	
	; 
	; there are 2 systems that can be used to operate the clock;
	; 1. generate 1 second period from the PIC 16MHz xtal
	; 2. generate 1 second period by counting mains freq pulses
	; (which is slected by jumper J2; ON = HI = mains freq)
	;-------------------------------------------------
	; first reset the TMR0 int flag
	bcf INTCON,T0IF		;

	; then test J2 to see which clock method is being used
	btfss PORTA,J2			; J2 HI = mains freq
	goto clock_xtal		;

	;-------------------------------------------------
	;-------------------------------------------------
clock_mains_freq

	; this system generates the 1 second period by simply
	; counting mains cycles; either 60 cycles (60Hz mains)
	; of 50 cycles (for 50Hz mains) =  1 second

	; check if a mains / edge was detected on either input pin
	; first, just check if either pin is hi
	movf PORTA,w			; read all pins on PORTA
	andlw b'00000110'		; keep only RA1 and RA2
	skpz					;
	goto cm_hi			; 

cm_lo
	; both pins are low
	clrf input_edge		; clear test flag
	goto button_test		; nothing more to do

cm_hi
	; one or more pin was high, so test if it was / edge
	btfsc input_edge,0		; test flag for zero
	goto button_test		; flag was already hi, so nothing to do

	; gets here on / edge (of either pin!)
	bsf input_edge,0		; set edge flag bit

	; now test for which pin it was
	btfss PORTA,Hz_60		;
	goto cm_50Hz			;

cm_60Hz
	; count one more mains cycle and see if 1 second reached
	decfsz hz_count,f		;
	goto button_test		; not 1 second, nothing more to do

	; gets here when 1 second reached!
	movlw d'60'			; load Hz counter again
	movwf hz_count			;
	goto reached_1second	;

cm_50Hz
	; count one more mains cycle and see if 1 second reached
	decfsz hz_count,f		;
	goto button_test		; not 1 second, nothing more to do

	; gets here when 1 second reached!
	movlw d'50'			; load Hz counter again
	movwf hz_count			;
	goto reached_1second	;

	;-------------------------------------------------
	;-------------------------------------------------
clock_xtal

	; clock system based on the 16MHz PIC xtal
	; This zero-error 1 second clock routine (see my web page)
	; will count +1 seconds for every 1 million TMR0 ticks.
	;
	; The LiniClock code then turns the stepper motor 1 microstep
	; for every 6 or 25 seconds, (depends on type of stepper motor)
	;-------------------------------------------------
	;-------------------------------------------------
	; zero-error 1 second clock here.

	; This consists of three main steps;
	; * subtract 256 counts from our 24bit variable
	; * test if we reached the setpoint
	; * if so, add 1,000,000 counts to 24bit variable and generate event.
	; (this code was copied from my "one_sec.asm" code)
	;-------------------------------------------------
						; * optimised 24 bit subtract here 
						; This is done with the minimum instructions.
						; We subtract 256 from the 24bit variable
						; by just decrementing the mid byte.

	tstf bres_mid			; first test for mid==0
	skpnz				; nz = no underflow needed
	decf bres_hi,f			; z, so is underflow, so dec the msb

	decfsz bres_mid,f		; dec the mid byte (subtract 256)

						; now the full 24bit optimised subtract is done!
						; this is almost 4 times faster than a "proper"
						; 24bit subtract.

	goto button_test		; nz, so definitely not one second yet.
						; in most cases the entire 'fake" int takes
						; only 9 instructions.
	;------------------------
						; * test if we have reached one second.
						; only gets here when mid==0, it MAY be one second.
						; only gets to here 1 in every 256 times.
						; (this is our best optimised test)
						; it gets here when bres_mid ==0.

	tstf bres_hi			; test hi for zero too
	skpz					; z = both hi and mid are zero, is one second!
	goto button_test		; nz, so not one second yet.

	;-------------------------------------------------
	; Only gets to here if we have reached one second.
						; Add the 1,000,000 ticks first.
						; One second = 1,000,000 = 0F 42 40 (in hex)

						; As we know hi==0 and mid==0 this makes it very fast.
						; This is an optimised 24bit add, because we can
						; just load the top two bytes and only need to do
						; a real add on the bottom byte. This is much quicker
						; than a "proper" 24bit add.

	movlw 0x0F			; get msb value 
	movwf bres_hi			; load in msb

	movlw 0x42			; get mid value
	movwf bres_mid			; load in mid

	movlw 0x40			; lsb value to add
	addwf bres_lo,f		; add it to the remainder already in lsb
	skpnc				; nc = no overflow, so mid is still ok

	incf bres_mid,f		; c, so lsb overflowed, so inc mid
						; this is optimised and relies on mid being known
						; and that mid won't overflow from one inc.

						; that's it! Our optimised 24bit add is done,
						; this is roughly twice as quick as a "proper"
						; 24bit add.
	;-------------------------
reached_1second	
	; Gets here every second. Now we can update the clock!
	; there are 2 speeds to suit the 2 possible motors.
	; dipwitch J1 on RA3 selects motor type; HI = 200step/rev motor

	btfss PORTA,J1			; test dipswitch J1
	goto clock_48			; is 48step/rev motor

	; gets here if a 200step/rev motor
	; need to advance motor 1 microstep every 6 seconds
clock_200

	incf second_count,f		; add a second
	movf second_count,w		; test for roll over >5
	sublw d'5'			; sub to test
	skpwgt				;
	goto pwm				; return, nothing to do yet

	; gets here every 6 seconds!
	clrf second_count		;
	goto make_a_step		; move motor!


	; gets here if a 48step/rev motor
	; need to advance motor 1 microstep every 25 seconds
clock_48

	incf second_count,f		; add a second
	movf second_count,w		; test for roll over >24
	sublw d'24'			; sub to test
	skpwgt				;
	goto pwm				; return, nothing to do yet

	; gets here every 25 seconds!
	clrf second_count		;
	goto make_a_step		; move motor!

make_a_step

	; for now just advance one microstep each second!
	; we are in 18th microstep mode, so step range is 0-71 (72 steps)
	incf step,f			; step++

	
	;movf step,w	; temp!! add a full step to w (is 18 counts)
	;addlw d'18'
	;movwf step



	movf step,w			; test for roll over >71
	sublw d'71'			; sub to test
	skpwgt				;
	goto move_motor		;
	

	clrf step				; wgt, rolled over so force to step 0

	;movlw 0x09			; temp!! rotate to full steps only
	;movwf step;



	goto move_motor		;

	;-------------------------------------------------
button_test

	; we get here roughly once for every TMR0 overflow
	; so we can test the clock set button and if it is set
	; advance the motor forward at a set speed.

	; note!! the dipswitch J1 on RA3 selects whether it is a
	; 48step or 200step motor. HI = 200 step

	btfss PORTA,J1			; test dipswitch J1
	goto button_test_48		; is 48step/rev motor

	;-------------------------
	; the clock set button is RA0; HI = set clock
	; this code below is for 200step/rev motor
button_test_200
	btfss PORTA,0			;
	goto button_low_200		;

button_high_200				; button is pressed!
	incf button_debounce,f	;
	movf button_debounce,w	; test for debounce >40
	sublw d'40'			; sub to test
	skpwgt				;
	goto pwm				; wle, just go back to pwm mode

	; is time to make a clock set step, to advance clock hand
	clrf button_debounce	; 
	goto make_a_step		;

button_low_200				; button is not pressed
	clrf button_debounce	; 
	goto pwm				; so return

	;-------------------------
	; the clock set button is RA0; HI = set clock
	; this code below is for 48step/rev motor
button_test_48
	btfss PORTA,0			;
	goto button_low_48		;

button_high_48				; button is pressed!
	incf button_debounce,f	;
	movf button_debounce,w	; test for debounce >150
	sublw d'150'			; sub to test
	skpwgt				;
	goto pwm				; wle, just go back to pwm mode

	; is time to make a clock set step, to advance clock hand
	clrf button_debounce	; 
	goto make_a_step		;

button_low_48				; button is not pressed
	clrf button_debounce	; 
	goto pwm				; so return


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




;******************************************************************************
; 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

	nop					;
	btfss INTCON,T0IF		; see if TMR0 overflowed yet!
	goto pwm_loop			; z, inputs not changed, so keep looping
						; (8 cycles)
	;-------------------------------------------------
						; TMR0 has overlfowed, so check if clock
						; hand needs to move (need to advance a step)
	goto update_clock		; 
	;-------------------------------------------------

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






;******************************************************************************
;  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'10000001'		;
		;  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		; (using 1:4 for Clock using 167MHz xtal)
						;
	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 0x09			; for step 9 of 0-71 (first full step position)
	movwf step			; loaded ready for jump table

	clrf bres_hi			; set up for 1 second clock
	movlw d'1'			;
	movwf bres_mid			;
	clrf second_count		;

	clrf button_debounce	;

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

  .