This isn't very clearly written code, but if you can get a grasp of what
it's trying to achieve, then porting it to a PIC ought to be trivial.
I hope the comments help a bit, if not mail me.

Regards

Mike Rigby-Jones

> Hi
> I have a problem, because I don«t know C- language !!!
> I wan«t to know how this C code works (it sends byte trough the parallel
> port to my Ti calculator, the link only has 3 wires and one is GND ).
>  I want to translate it to PIC, so I can interface my Ti with the PIC
> Anything would help, just a few comnents and I«ll try to figure out the
> rest
> Thanks for you time
> Javier
> 
> /*
>    * Sends a byte to the calculator
>    */
>   int put92(char data)                /* function put92, accepts a char(1
> byte in PC terms) and returns an int (16 bit word)
>   {
>     int bit;                                  /* declares a 16 bit
> variable called bit */
>     for (bit=0; bit<8; bit++) {     /* loop using bit as a counter.  bit
> is incremented for each loop iteration until  bit = 8 */
>       if (bit==1) tx(1);                  /* when bit=1 then function
> tx is called passing an argument off 1.  You don't seem to have this
> function */
>       if (data&1) {                           /* is bit 0 of variable
> 'data' set ?*/
>         outportb(lpt_out, 2); /*  Yes it is.  Output a value of 2 to the
> printer port (sets bit 1) */
>         while (inportb(lpt_in)&0x10); /* read port lpt_in and loop while
> bit 5 is set */
>         outportb(lpt_out, 3);                 /* outputs 3 to the printer
> port (sets bits 0 and 1) */
>         while ((inportb(lpt_in)&0x10)==0x00); /* read port lpt_in and loop
> while bit 5 is not set */
>       } else {
>         outportb(lpt_out, 1); /* bit 0 of data is NOT set, output a 1 to
> the printer port. (sets bit 0) */
>         while (inportb(lpt_in)&0x20); /* read port lpt_in and loop while
> bit 6 is set */
>         outportb(lpt_out, 3);                 /* output 3 to the printer
> port, (sets bits 0 and 1) */
>         while ((inportb(lpt_in)&0x20)==0x00);     /* read port lpt_in and loop
> while bit 6 is not set */
>       }
>       data>>=1;                                             /* shift
> data right one place, roughly equivavlent to RRF on pic */
>       // may need 10us delay here
>     }
>   }
> 
> 
>   /*
>    * Reads a byte from the calculator
>    */
>   unsigned char get92(void)                   /* function get92 accepts no
> arguments and returns an unsigned char (8 bit byte) */
>   {
>     int bit;                                                  /* declare
> 16 bit variable 'bit' */
>     unsigned char data=0, v;                        /* declare 8 bit variabl
es
> 'data' and 'v'.  Data is initialised to 0*/
>     for (bit=0; bit<8; bit++) {                     /* set up loop as
> before */
>       while ((v=inportb(lpt_in)&0x30) == 0x30); /* read port lpt_in
> and puts result in v.  Loops while bits 4 and 5 are set; */
>       if (v==0x10) {                                      /* is v = 0x10
 ? */
>         data=(data>>1)|0x80;                        /* yes, shift data right
 one
> place and OR the result with 0x80;
>         outportb(lpt_out, 1);                 /* output 1 to printer port
> (sets bit 0)
>         while ((inportb(lpt_in)&0x20)==0x00); /* read port lpt_in and loop
> while bit 5 is clear */
>         outportb(lpt_out, 3);                 /* output 3 to printer port
> (sets bits 0 and 1) */
>       } else {                                                        /*
> no, v is not equal to 0x10 */
>         data=data>>1;                                       /* shift 'data'
> right one place */
>         outportb(lpt_out, 2);                 /* output 2 to lpt_out (sets
> bits 0 and 1) */
>         while ((inportb(lpt_in)&0x10)==0x00); /* read port lpt_in and loop
> while bit 4 is clear */
>         outportb(lpt_out, 3);                 /* output 3 to printer port
> (sets bits 0 and 1) */
>       }
>       // may need 10us delay here
>     }
>     return data;                                              /* returns
> data to calling function */
>   }