The memory mapped address is defined in the configuration of Or1ksim (see Section 5.6) to be 0x90000000. This is set as a defined constant in the test program.

#define BASEADDR  0x90000000
	  

The memory mapped structure consists of a byte, half word (16 bits) and full word (32 bits), all declared as volatile within the struct. These are all declared with the C types, which for the OpenRISC 1000 tool chain are known to correspond to these sizes.

struct  testdev
{
  volatile unsigned char       byte;
  volatile unsigned short int  halfword;
  volatile unsigned long  int  fullword;
};
	  

The main program declares a pointer to this struct at the BASEADDR, along with 3 variables to hold the results of the various sized results when reading.

main()
{
  struct testdev *dev = (struct testdev *)BASEADDR;

  unsigned char       byteRes;
  unsigned short int  halfwordRes;
  unsigned long int   fullwordRes;