Counters using the delay routine.

Introduction

I get lots of emails and PM to write some more Assembly language programs and as I have some time I thought of writing some more.

Its called Counters using the delay routine.

Subroutine

The subroutine we will use is as follows. This will behave as a delay for our counter

Code:

//FUNC
   MVI C, FF
   // Load Register C with the Hex value FF
   DCR C
   // Decrement the C Register // Address of the statment is XXXX
   JNZ XXXX
   // loop till you get the counter reduced to zero
   RET

Now we will write the actual program to have the counter

Code:

   LXI SP, 87DD
   // Load immediate stack pointer
   LXI H, 0000
   // Load immediate register Pair H & L
   MVI B, 10
   // Load Register B with the Hex value 10
   SHLD 87FD
   // Store H & L direct
   PUSH B
   // Push register Pair B & C on stack
   CALL FUNC
   // Call the above subroutine
   POP B
   // Pop register Pair B & C off stack
   DCR B
   // Decrement B
   JNZ XXXX // - SHLD Location
   // Jump on no zero
   INX H
   // Increment H & L registers
   JMP XXXX // MVI B 10 location
   // Jump unconditional

Now to make the decrement counter you just need one change INX to DCX

 

Just remove the CALL statement and that should be fine.

 

Removing the CALL leaves you with the counter. specially the

Code:

   DCR B
   // Decrement B
   JNZ XXXX // - SHLD Location
   // Jump on no zero
   INX H
   // Increment H & L registers

 

Looping till non zero by decrementing it.