/* Output ports 
   Last updated 14.4.00
 */

/* The state of the output ports can be controlled through an 
   8 bit memory mapped register at address 0xf000. Each port 
   is controlled by 2 bits as follows:

   Port A bits 7-6
   Port B bits 3-2
   Port C bits 1-0

   The four different values for each 2 bit value controls 
   the port as follows:

   00  disconnect port from power supply
   01  allows current in one direction
   10  allows current in the other direction
   11  connect the port to the same polarity of the supply

 */

#define OutputPorts    *(( volatile byte *) 0xf000 )

#define Amask 0xc0    
#define Bmask 0x0c     
#define Cmask 0x03     

#define Float 0
#define OnPos 1
#define OnNeg 2
#define Brake 3

void PortA( byte state )
{
  byte temp;

  temp  = OutputPorts;
  temp &= ~Amask;
  temp |= (state << 6);
  OutputPorts = temp;
}

void PortB( byte state )
{
  byte temp;

  temp  = OutputPorts;
  temp &= ~Bmask;
  temp |= (state << 2);
  OutputPorts = temp;
}

void PortC( byte state )
{
  byte temp;

  temp  = OutputPorts;
  temp &= ~Cmask;
  temp |= (state << 0);
  OutputPorts = temp;
}