In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Lightfoot wrote:

The following program generates pulses on the RB.0 pin.  The circuit uses a mosfet transistor to amplify the pulses for electric motor control.  For speed adjustment, it takes a value on the RA port and converts it into pulse widths.  It supports ten speeds including a full off (zero).  Is their a way to shorten it?

[code]
DEVICE          SX18, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ            4_000_000

tris_b = 0 'Set RB port to outputs
plp_a = 0 'Enable pullup resistors for RA port
lowdur var byte 'Stores the length of time the signal is low.
ctr var byte 'Incrementing variable for loops.

Main:

if ra = 15 then 'The default value is 15 hence the pullups are enabled.
	rb.0 = 0 'Signal is completely low.
	goto Main 'Infinate loop.
endif
if ra = 0 then 'Zero represents the same value as 15.
	rb.0 = 0 'Signal is completly low.
	goto Main 'Infinate loop.
endif
if ra = 10 then 'Ten represents motor running at full speed.
	rb.0 = 1 'Signal is completely high.
	goto Main 'Infinate loop
endif

lowdur = 10 - ra 'Calculate the time the signal is low.

rb.0 = 1 'Enable RB.0 which is the PWM pin.

for ctr = 0 to ra 'Loop number of times pulse is high.
	pauseus 100 'Wait 100 microseconds.
next ctr

rb.0 = 0 'Disable RB.0

for ctr = 0 to lowdur 'Loop number of times pulse is low.
	pauseus 100 'Wait 100 microseconds.
next ctr

goto Main 'Infinate loop
[/code]

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