3.6. Data Directives

The .byte, .word, .dword and .text directives are used to generate byte, word (one word= two bytes), dword (double word = 4 bytes) and text data as in standard 65xx assemblers. 

.byte 1,2,3,4      // Generates the bytes 1,2,3,4
.word $2000,$1234  // Generates the bytes $00,$20,$34,$12
.dword $12341234   // Generates the bytes $34,$12,$34,$12
.text "Hello World"

You can use .by, .wo and .dw as aliases for .byte, .word and .dword, so '.by $10' is the same as '.byte $10'.

With the .fill directive you can fill a section of the memory with bytes. It works like a loop and automatically sets the variable i to the iteration number. 

// Nomal filling
.fill 5, 0 // Generates byte 0,0,0,0,0
.fill 5, i // Generates byte 0,1,2,3,4
.fill 256, 127.5 + 127.5*sin(toRadians(i*360/256)) // Generates a sine curve

// Use [,,] to fill with a repeat pattern
.fill 4, [$10,$20]             // Generates .byte $10,$20,$10,$20,$10,$20,$10,$20
.fill 3, ['D','E','M','O','!'] // Generates the same bytes as .text "DEMO!DEMO!DEMO!"
.fill 3, [i,i*$10]             // Generates .byte 0,0,1,$10,2,$20

// .fillword is like .fill but with .word directives 
.fillword 5,i*$80      // Generates .word $0000,$0080,$0100,$0180,$0200
.fillword 2,[$100,0]   // Generates .word $0100,$0000,$0100,$0000

In most cases it is more desirable to have two lists, one with low byte and one with high byte, than a word list. To generate this you can use the .lohifill directive. It generates the two list right after each each other and lets your access them using a hi/lo field on a connected label like this: 

       ldx #20   // ychar coord
       ldy #15   // xchar coord
       clc
       lda mul40.lo,x  // Access lo byte table
       sta $fe
       lda mul40.hi,x  // Access hi byte table
       ora #$04
       sta $ff
       lda #'x'
       sta ($fe),y     // Draws 'x' at screenpos x,y
       rts


mul40: .lohifill $100, 40*i    // Generates lo/hi table: 
                               // .byte <0, <40, <80, <120, ....
                               // .byte >0, >40, >80, >120, ....

Generating bytes using the fill directive will compile faster than generating byte using the .for and .byte directives. (The .for directive will be explained later.)

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