8051 Code

[Mungovan]

Hi.
Basically I need to implement the following code on an 8051 microcontroller:

If X < 10 THEN A<=B
ELSE A<=C

Does anyone know how this might be achieved. I know it has to so with conditional jump statements, but just not exactly how....

Any help would be greatly appreaciated

Thanks,
D

 

[RCallaway]

Mungovan,
For the < 10 I always check z and c flags after a cjne instruction. For the <= stuff, is that a pascal format for A = C, or the 'C' format for &quot;A = A shifted C times&quot;? If the real question is the < 10, let me know, I have many macros made for ==, <=, <, >, >=, ect. Including seperate macros for those pesky long jumps!!! i.e. if x < 10 jump really far away...
RCallaway

 

[barbari]

what is it &quot;X&quot; ?

mov A,X
subb X, #10h
jnc st
mov A,B
sjmp end
st:mov A,C
end: bla bla

 

[RCallaway]

barbari - Are you sure the carry flag is cleared before the subb instruction? I don't think mov a,x clears it. Also you have #10h, it should be decimal.... (typo)
Here is what I do:

cjne a, #10, Lab_x ; Modify carry flag
Lab_x: jnc NotLessThan
ajmp LessThan
NotLessThan: mov a, b
sjmp TheEnd
LessThan: mov a, c
TheEnd:

Note -- be careful with the b, it's a real 8051 register..

Here is my macro, which gets rid of the bulky labels...
cjl MACRO X_, Y_, REL
cjne X_, Y_, $ + 3
jnc $ + 4
ajmp REL
ENDM

cjl a, #10, LessThan
mov a, b
sjmp theend
LessThan: mov a, c
theend: