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Branching and Looping. Chapter 5. Branching and Looping. 68HC12 Branch Instructions WHYP Branching and Looping Words Recursion in WHYP. Branch Displacement. Negative Branch. Branch on Z flag. Branch on Z flag. Branch on Z flag. Branch on N flag. Branch on N flag.

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Branching and looping2 l.jpg
Branching and Looping

  • 68HC12 Branch Instructions

  • WHYP Branching and Looping Words

  • Recursion in WHYP













Branching and looping17 l.jpg
Branching and Looping

  • 68HC12 Branch Instructions

  • WHYP Branching and Looping Words

  • Recursion in WHYP


Whyp branching and looping words l.jpg
WHYP Branching and Looping Words

  • IF…ELSE…THEN

  • FOR…NEXT

  • BEGIN…AGAIN

  • BEGIN…WHILE…REPEAT

  • DO…LOOP




Slide23 l.jpg

TRUE = -1

FALSE = 0



If else then l.jpg
IF…ELSE…THEN

<cond> IF <true statements> ELSE <false statements> THEN


Slide26 l.jpg

TRUE iftest

true statements

next statements

FALSE iftest

next statements


Slide27 l.jpg

TRUE if.else.test

true statements

next statements

FALSE if.else.test

false statements

next statements



For next loop l.jpg
FOR…NEXT Loop

n FOR <WHYP statements> NEXT



For next delay loop l.jpg
FOR…NEXT Delay Loop

8 MHz clock: #ms = #clock_cycles/8 = 7.75 +1.375*N

N = (#ms - 7.75)/1.375

Ex: 50 ms delay: N = (50000 - 7.75)/1.375 = 36358


Longer delays l.jpg
Longer Delays

Note: A 10 second delay on the MC68HC12A4EVB

takes about 17 seconds because one wait state

has been added to each access to external RAM.

The 68HC11 takes over twice as long to execute

the same delay instructions.


Begin again l.jpg
BEGIN…AGAIN

BEGIN <WHYP statements> AGAIN


Begin until l.jpg
BEGIN…UNTIL

BEGIN <WHYP statements> <flag> UNTIL


Begin while repeat l.jpg
BEGIN…WHILE…REPEAT

BEGIN <words> <flag> WHILE <words> REPEAT





Do loop l.jpg
DO…LOOP

<limit> <index> DO <WHYP statements> LOOP

Moves <limit> and <index>

to return stack

Increments <index> on return stack

and loops back to <WHYP statements>

if <index> is less than <limit>,

else pop <limit> and <index> from

return stack and exit loop


Slide47 l.jpg

DO…LOOP

The WHYP word I copies the index value from

the return stack to the top of the parameter stack.

: test ( -- )

11 1 DO

I .

LOOP ;

will print

1 2 3 4 5 6 7 8 9 10



The word leave l.jpg
The Word LEAVE

Exits a DO loop prematurely


Branching and looping51 l.jpg
Branching and Looping

  • 68HC12 Branch Instructions

  • WHYP Branching and Looping Words

  • Recursion in WHYP


Recursion in whyp l.jpg
Recursion in WHYP

n! = n * (n - 1)!



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