Branching and Looping

1. Branching and Looping Chapter 5

2. Branching and Looping • 68HC12 Branch Instructions • WHYP Branching and Looping Words • Recursion in WHYP

4. Branch Displacement

5. Negative Branch

7. Branch on Z flag

8. Branch on Z flag

9. Branch on Z flag

10. Branch on N flag

11. Branch on N flag

12. Branch on C and V flags

13. Bit-Condition Branch Instruction

15. How many times is the instruction INCB executed?

16. Signed Branch Instructions

17. Branching and Looping • 68HC12 Branch Instructions • WHYP Branching and Looping Words • Recursion in WHYP

18. WHYP Branching and Looping Words • IF…ELSE…THEN • FOR…NEXT • BEGIN…AGAIN • BEGIN…WHILE…REPEAT • DO…LOOP

21. 68HC12 Code for <

22. 68HC12 Code for U<

23. TRUE = -1 FALSE = 0

24. 68HC12 Code for AND

25. IF…ELSE…THEN <cond> IF <true statements> ELSE <false statements> THEN

26. TRUE iftest true statements next statements FALSE iftest next statements

27. TRUE if.else.test true statements next statements FALSE if.else.test false statements next statements

28. IF…ELSE…THEN Example

30. FOR…NEXT Loop n FOR <WHYP statements> NEXT

31. : stars for ." *" next ;

32. 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

34. 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.

35. BEGIN…AGAIN BEGIN <WHYP statements> AGAIN

36. BEGIN…UNTIL BEGIN <WHYP statements> <flag> UNTIL

39. BEGIN…WHILE…REPEAT BEGIN <words> <flag> WHILE <words> REPEAT

42. Sine and Arcsine

43. Sine and Arcsine

44. Sine and Cosine

46. 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

47. 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

48. DO…LOOP Example

49. The Word LEAVE Exits a DO loop prematurely