Carlos Gruber wrote:

I can not get precise timing using
>  the Intel instruction set
> because I don't know how long is each instruction and how many clock cycles
 are
>  necesary for its ejecution. In
> the data sheet of 8086 family are a brief instruction set sumary but it not
>  include information detailed
> (Syntax, operands, operation, status affected, encoding, description, words,
>  cycles, and examples)
>
Somebody of your know a list, usenet or a web addres useful for me?
>

Carlos,

I do not recommend that you use SW loops that depend on instruction
clock cycles for your timing loops. This is very complex in with an
Intel CPU because of the instruction piplining, memory wait states and
varying clock speeds. There are three better ways.

1) Learn to use one of the PCs internal timers to produce an interrupt
at known intervals. You will need to dig into the PC HW and Peripheral
chip programming specs for this. I have used this method in a DOS
application successfully many years ago and do not remember all of the
details. If you choose to go this route and have specific questions, I
can help you.

2) Put a convenient reference clock on your external circuit and connect
it to a Parallel port input pin so that it can be polled. Your SW can
count multiples of this clock rising and falling to create longer
delays. Steve Marshon does this on his PIC16C84 programmer. I have used
this in one of my projects as well.

3) Same as two, but connect the signal to a parallel port pin that can
generate an IRQ to the PC on each clock cycle.


I am sorry that I cannot be more specific without going back and doing
some research. If you tell me more about your application, I can help
you some more.

1) How many of the pins on the port must you use for your application.
(Ins and Outs)

2) What kind of time delays are you looking for.

3) Are you building the external HW, or are you stuck with something
that exists.

4) Is your program DOS or Windows? (3.1, 95, or NT).

Good Luck
John Montalbano