DDRD  &= ~(_BV(PD2));                            // Назначаем 2-ю линию порта D на вход
  PORTD |=  (_BV(PD2));                            // подключаем "подтягивающий" резистор

//определяем частые действия
#define cs_active   PORTD &=~(_BV(PD2))
#define cs_inactive   PORTD |=_BV(PD2)
...

//используем
cs_active;

...

cs_inactive;
...

#define bitset(var,bitno) ((var) |= 1 << (bitno))
#define bitclr(var,bitno) ((var) &= ~(1 << (bitno)))
bitclr(DDRD, PD2);
bitset(PORTD, PD2);

typedef mytype
union
{
   uchar i;
   struct
   {
      uchar _0: 1;
      uchar _1: 1;
      ...
   } b;
}

union
{
   uchar i;
   struct
   {
      uchar Out0: 1;   // естественно, лучше дать осмысленное имя
      ...
   } b;
} PortAOut;

/* GPIO Bits */
static volatile bit    GPIO0    @ (unsigned)&GPIO*8+0;

#define LED_DDR              DDRD
#define LED_PORT             PORTD
#define LED_PIN                PIND
#define LED                       3
#define LED_ON                 LED_PORT |= (1<<LED)
#define LED_OFF                LED_PORT &= ~(1<<LED)

    if(system.led_timer == 0)
    {
      if((LED_PIN & (1<<LED)) == 0)
      {
        LED_ON;
      }
        else
        {
          LED_OFF;
        }

      system.led_timer = 0.1*(1000/SYSTEM_TICK);
    }

#define PRG_RDB(addr)   (*(PROGMEM char *)(addr))

        PORTD |= ( 1 << 1 );  
  d2:    91 9a           sbi    0x12, 1           ; 18

        PORTD |= ( 1 << 1 );  
  de:    a2 e3           ldi    r26, 0x32; 50
  e0:    b0 e0           ldi    r27, 0x00; 0
  e2:    e2 e3           ldi    r30, 0x32; 50
  e4:    f0 e0           ldi    r31, 0x00; 0
  e6:    80 81           ld    r24, Z
  e8:    82 60           ori    r24, 0x02; 2
  ea:    8c 93           st    X, r24

;PORTD |= ( 1 << 1 );  
00007e 9a91          SBI  0x12,1

;PORTD.1 = 1;  
00007f 9a91          SBI  0x12,1

PORTD = ( 1 << 0 );  
PORTD = ( 1 << 1 );
PORTD = ( 1 << 2 );  
PORTD = ( 1 << 3 );
PORTD = ( 1 << 4 );  
PORTD = ( 1 << 5 );
PORTD = ( 1 << 6 );  
PORTD = ( 1 << 7 );

int main(void)
{
  ce:    71 e0           ldi    r23, 0x01; 1
  d0:    62 e0           ldi    r22, 0x02; 2
  d2:    54 e0           ldi    r21, 0x04; 4
  d4:    48 e0           ldi    r20, 0x08; 8
  d6:    30 e1           ldi    r19, 0x10; 16
  d8:    20 e2           ldi    r18, 0x20; 32
  da:    90 e4           ldi    r25, 0x40; 64
  dc:    80 e8           ldi    r24, 0x80; 128

    while(1)
    {
        PORTD = ( 1 << 0 );  
  de:    72 bb           out    0x12, r23; 18
        PORTD = ( 1 << 1 );
  e0:    62 bb           out    0x12, r22; 18
        PORTD = ( 1 << 2 );  
  e2:    52 bb           out    0x12, r21; 18
        PORTD = ( 1 << 3 );
  e4:    42 bb           out    0x12, r20; 18
        PORTD = ( 1 << 4 );  
  e6:    32 bb           out    0x12, r19; 18
        PORTD = ( 1 << 5 );
  e8:    22 bb           out    0x12, r18; 18
        PORTD = ( 1 << 6 );  
  ea:    92 bb           out    0x12, r25; 18
        PORTD = ( 1 << 7 );
  ec:    82 bb           out    0x12, r24; 18

        ;      34         PORTD = ( 1 << 0 );  
00007a e0e1          LDI  R30,LOW(1)
00007b bbe2          OUT  0x12,R30
        ;      35         PORTD = ( 1 << 1 );
00007c e0e2          LDI  R30,LOW(2)
00007d bbe2          OUT  0x12,R30
        ;      36         PORTD = ( 1 << 2 );  
00007e e0e4          LDI  R30,LOW(4)
00007f bbe2          OUT  0x12,R30
        ;      37         PORTD = ( 1 << 3 );
000080 e0e8          LDI  R30,LOW(8)
000081 bbe2          OUT  0x12,R30
        ;      38         PORTD = ( 1 << 4 );  
000082 e1e0          LDI  R30,LOW(16)
000083 bbe2          OUT  0x12,R30
        ;      39         PORTD = ( 1 << 5 );
000084 e2e0          LDI  R30,LOW(32)
000085 bbe2          OUT  0x12,R30
        ;      40         PORTD = ( 1 << 6 );  
000086 e4e0          LDI  R30,LOW(64)
000087 bbe2          OUT  0x12,R30
        ;      41         PORTD = ( 1 << 7 );                 
000088 e8e0          LDI  R30,LOW(128)
000089 bbe2          OUT  0x12,R30

PORTD = ( 1 << 0 );
  fc:    81 e0           ldi    r24, 0x01; 1
  fe:    8b b9           out    0x0b, r24; 11
PORTD = ( 1 << 1 );
100:    82 e0           ldi    r24, 0x02; 2
102:    8b b9           out    0x0b, r24; 11
PORTD = ( 1 << 2 );
104:    84 e0           ldi    r24, 0x04; 4
106:    8b b9           out    0x0b, r24; 11
PORTD = ( 1 << 3 );
108:    88 e0           ldi    r24, 0x08; 8
10a:    8b b9           out    0x0b, r24; 11
PORTD = ( 1 << 4 );
10c:    80 e1           ldi    r24, 0x10; 16
10e:    8b b9           out    0x0b, r24; 11
PORTD = ( 1 << 5 );
110:    80 e2           ldi    r24, 0x20; 32
112:    8b b9           out    0x0b, r24; 11
PORTD = ( 1 << 6 );
114:    80 e4           ldi    r24, 0x40; 64
116:    8b b9           out    0x0b, r24; 11
PORTD = ( 1 << 7 );
118:    80 e8           ldi    r24, 0x80; 128
11a:    8b b9           out    0x0b, r24; 11
PORTD |= ( 1 << 0 );
11c:    58 9a           sbi    0x0b, 0; 11
PORTD |= ( 1 << 1 );
11e:    59 9a           sbi    0x0b, 1; 11
PORTD |= ( 1 << 2 );
120:    5a 9a           sbi    0x0b, 2; 11
PORTD |= ( 1 << 3 );
122:    5b 9a           sbi    0x0b, 3; 11
PORTD |= ( 1 << 4 );
124:    5c 9a           sbi    0x0b, 4; 11
PORTD |= ( 1 << 5 );
126:    5d 9a           sbi    0x0b, 5; 11
PORTD |= ( 1 << 6 );
128:    5e 9a           sbi    0x0b, 6; 11
PORTD |= ( 1 << 7 );