Ab Lbl Instruction

HI
please open up the PDF file and my question is why LBL instruction is without JMP Many Regards PERSI

There's a jump in rung 4.

Keith

HI KEITH
Thanks for the reply sorry I did not see jmp in rung for I thought that jmp is first and lbl is placed in the program after jmp instruction thanks anyway.

This method of jumping backwards is useful for a VERY LIMITED and tightly controlled number of times. Otherwise an endless loop could be established faulting the processor with a watchdog timeout. It is generally not suggested and, if the nubmer of repitions is small, just repeat the code.

WOW! Talk about doing things the hard way! That code is guaranteed to generate a 3:00 am phone call from Bubba.

It takes bits 2, 3, 4, and 5 from input word I:0.0 and puts them at bits N7:0, N7:1, N7:2, and N7:3 so that a single digit BCD value can be placed in N7:1. It does this by copying the input word to N7:0 and then bit sifting N7:0 right two times with a for loop.

First off, when you want to shift bits right just divide by 2^n where n is the number of places you want to shift. Dividing N7:0 by 4 will shift all the bits in N7:0 right by 2 places. Use the bit shift instruction when you want to shift in a bit.

But in this case the solution is even more simple.

 I:0/2           N7:0/0

---] [------------( )----

 

 I:0/3           N7:0/1

---] [------------( )----

 

 

 I:0/4           N7:0/2

---] [------------( )----

 

 I:0/5           N7:0/3

---] [------------( )----