pin in/out at top speed

TCP71

Once again, please forgive my ignorance.
I am trying to test an input pin for a specific state and then toggle another pin as quickly as possible once the state has been reached. What is the fastest method to have this happen. It seems that waitpeq in spin code, followed by an "outa" instruction seems to take almost 9uS to occur. This is probably completely simple to do in assembly, but I'm the furthest thing from a programmer you can imagine. Any (simple?) ideas would be appreciated.

tonyp12

So you want to do it in spin.

I wonder if you can set up the counter in spin, in a set and forget?
I'm not sure, as I'm a assembler dude.

Logic modes of operation
Modes %10000 through %11111 operate differently that the other modes of operation.
In these Logic modes, APIN and BPIN are inputs into the counter which dictate when
the FRQA register is added into the PHSA register.
Only when the logic equation specified by the mode is true is the FRQA
register added to the PHSA register.

The %10000 (LOGIC never) mode is equivalent to mode
%00000 (Counter off), since the FRQA register is never added to the PHSA register.
The %11111 (LOGIC always) mode is similar to the system clock in that the FRQA
register is added to PHSA register every cycle.

The remaining modes accumulate when the mode’s logic equation evaluates as
true. These modes operate on buffered inputs, so the values present at the APIN
and BPIN of the previous clock cycle are used in the equation for the present clock cycle.

Beau Schwabe

You should be able to do this with the counters...

Set one counter to your desired "toggle ... as quickly as possible" ... this can be up to 125MHz

Set another counter pointing to the same output pin as a 'POS detector with feedback' or 'NEG detector with feedback' depending on the pin state you want to look for. ... <-- you could do this using the ina and dira but the time required to execute ina and dira in SPIN would defeat the purpose. The way that the dir and out registers are OR'd ... 'POS detector with feedback' is the proper way to do this.

ElectricAye

Beau Schwabe (Parallax) wrote: »

You should be able to do this with the counters... ..

You might look at this attached info on counters.

Beau Schwabe

Here is a small test program written in SPIN that uses both counters and completely runs in the background. If the input pin is pulled down to Vss with a 1k resistor or so, then a HIGH signal on the pin will enable the output pin with a 10kHz square wave.

CON
  _CLKMODE = XTAL1 + PLL16X
  _XINFREQ = 5_000_000

Input_Pin         = 1           { Event detector } 

Output_Pin        = 0
Output_Frequency  = 10000       { in Hertz }
Output_Counter    = "A"         { Use Counter A to generate output frequency }

OBJ
Hz           : "Synth"

PUB Demo
    Hz.Synth(Output_Counter,Output_Pin,Output_Frequency)
    ctrb := %01001 << 26        { POS detector with feedback }
    ctrb |= Output_Pin << 9     { Set 'Bpin' as the defined output pin }
    ctrb |= Input_Pin           { Set 'Apin' as the defined input pin }

    repeat

TCP71

Thanks. I will look at the counters a bit closer. Sorry Tony, that may as well have been Swahili. Beau, I will work on trying to understand what you've done in the program above and apply it to my code. I really just need to monitor pin 0, when it goes to ground, i need to set pin 5 high ASAP. That's it. I really appreciate all your help.