Bit Banging input to output on PIC16F876A

[Bronurstomp]

Hi folks.
Some init stuff: I'm using a PIC16F876A.

DEFINE OSC 20 ' use 20mhz xtal.
DEFINE HPWM1_TMR 1 'Use timer 1 for both channels
DEFINE HPWM2_TMR 1
DEFINE CCP1_REG PORTC 'Hpwm 1 pin port
DEFINE CCP1_BIT 2 'Hpwm 1 pin bit

I want to output a bit on PORTB.2. Ok np.
Now I want to logically AND it to the input pulse on PORTA.2 and send it to another pin, say PORTB.6. The input pin PORTA.2 is electrically connected to HPWM pin (output) of this same chip. I want to basically multiplex the PWM output to other output pins via the logical AND. I've generated the HPWM before calling this subroutine.

If (stuff happens)
HPWM 1, percntpwm, 3000 REM ----- 3KHZ output for example. How fast can this be?

Gosub Bitbang

This is the subroutine I'm thinking of using. It seems pretty straight forward, but can it be done like this?

Bitbang:
PORTB.1 = 0 ; These outputs
PORTB.2 = 1 ; are also needed
PORTB.3 = 1
PORTB.4 = 0

PORTB.6 = PORTA.2 AND PORTB.2 ; Perform AND then route the result to the output

RETURN

I'm away from my hardware for a few months on business so I can't test this idea.
The real question is: What is the highest HPWM frequency I can accurately reproduce on the PORTB.6 output assuming a 20MHZ Crystal?
Thanks in advance!

[Melanie]

So why not go a stage further...

Chose a PIC that not only has Hardware PWM, but also a Hardware Comparator (eg 16F628) with dedicated output. Cross Connect the HPWM to one Comparator Input. The 2nd Comparator Input is cross connected to the PIC pin of your choice. This pin now ANDs (modulates) the Comparator (PWM Carrier) output. Not much need to bit-bang anything... and almost no software overhead...

Life is simple (or at least it can be)...

[mister_e]

The real question is: What is the highest HPWM frequency I can accurately reproduce on the PORTB.6 output assuming a 20MHZ Crystal?
Thanks in advance!

Well, i really depend of the accuracy you can/want to deal with. PICMultiCalc says you can produce up to 2.5 MHz @ 20MHz.. but <4 bit resolution... only 8 duty steps

To do so, you'll need to configure the CCP registers manually.

[Bruce]

Melanie,

I would love to see an example of how this works. It would be really nice for sending IR serial
data modulated at 38-40kHz.

[Melanie]

Give me a couple of days Bruce to find some spare time and throw an example together - I'll post it here... watch this space...

[mister_e]

7 days a week, 24 hours a day, you only work 120 hours a week... so you still have spare time huh?

I see what's you're cooking. I've used something like that in the past... before i lost everything on my hard drive

I remember that i also modified SEROUT routine... and it also remember me something that Darrel already did here... i'll search for it now.

[Bruce]

I've tried what Melanie mentioned, but could never get it to work properly when changing
Vref with another I/O-pin.