[openrisc] First steps

["Michael McAllister" <mmcallister@annapmicro.com>]

I am working on getting the OpenRISC 1200 (ORPsoc from the Xess Xsv-800
demo) running on a Virtex 2000E-based FPGA board.  This board also has
SRAM & a serial port.  The hardware & firmware guys have successfully
synthesized and place & routed the microprocessor in the Viretx FPGA
with the UART IP Core and w/o the MMU; it's my job to get the s/w
working.

I have the ability to read & write SRAM from a host computer,
independent of the FPGA.  My thought was to get a "hello world" kind of
program running by loading the program into the FPGA board's SRAM,
loading the FPGA with the OpenRISC processor, taking the processor out
of reset, and seeing it write HELLO out to the serial port in an endless
loop.  For this initial test, I thought it might be easier if I write
some code that directly sets up the UART, and NOT try to get uCLinux up
and running right away (though that is the eventual goal).

I am told by the firmware guy that the UART is at address 0x90h.  I have
recompiled the GNU tools & DDD & uCLinux & uclibc, etc, on a Linux box.
I am wondering if I can just write a simple 'C' program:

#define SERIAL_PORT_DATA    0x00000090ul   /* Serial Prot Data Register
*/
#define SERIAL_PORT_CONTROL 0x00000093ul   /* Line Control Register
(LCR) */

int main ()
{
  char *pDataPort;
  char *pControlPort;

  pControlPort = SERIAL_PORT_CONTROL;
  pDataPort    = SERIAL_PORT_DATA;

  *pControlPort = 0x10; /* Set the LCR divisor latch (DL) bit */
  *(pDataPort+2)= 0x0;
  *(pDataPort+1)= 0x41; /* LSB of DL is set; internal counter starts */
  *pControlPort = 0x0;  /* Clear the LCR divisor latch bit */

  while (1)  {
    *pDataPort = 'H';       /* Send hello forever */
    *pDataPort = 'e';
    *pDataPort = 'l';
    *pDataPort = 'l';
    *pDataPort = 'o';
    *pDataPort = '\r';
  }

  return(0);
}

Load it into the SRAM, and see it start writing data to the output TX
line?

Any ideas if this will work?  What intermediary steps must be done to
the "a.out" ELF file from gcc... is there a utility to convert it to
plain old machine code that can be directly executed? Is there a "newbie
FAQ"?  If not, I am volunteering to write one about my experiences.


Sincerely,
Michael McAllister

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