disable/enable interrupts to stop the bios from reading the keyboard

before we have the chance to do it...

diff --git a/bb.asm b/bb.asm
index 3f4bcd1..d9d1fe6 100644 (file)
--- a/bb.asm
+++ b/bb.asm
@@ -37,17 +37,6 @@ start:
        mov ax, 3
        call clearscreen
 
-; waiting for keypress
-; x86 has 2 special instructions to read/write from I/O
-; devices: in and out (because some processors have different
-; address spaces for devices and for memory, arm not)
-.key_wait:
-       in al, 64h      ; 60h = keyb data port, 64h = keyb status port
-       and al, 1       ; 1 = OUTBUF_FULL = the keyb controller out buf is full
-       jz .key_wait
-
-       in al, 60h      ; reads the keyb that was pressed to reset the flag
-
 ; load 2nd sector from boot device and jump to it
 ; bios helpers, 13h = disk io
        mov ax, 0
@@ -143,5 +132,42 @@ sector_2:
        test al, 3fh    ; test with 3fh to keep the lowest 6 bits of al
        jnz .pal_loop
 
+; disable all interrupts (for bios to not read the keyboard)
+       cli
+
+main_loop:
+       mov ax, 0a000h
+       mov ds, ax
+       xor bx, bx              ; mov bx, 0 to clear the register
+.static_loop:
+       call rand
+       and ax, 3fh             ; last six bits of eax (see rand)
+       mov [bx], al
+       inc bx
+       cmp bx, 64000   ; num pixels
+       jnz .static_loop
+
+       in al, 64h              ; 60h = keyb data port, 64h = keyb status port
+       and al, 1               ; 1 = OUTBUF_FULL = the keyb controller out buf is full
+       jz main_loop    ; no key pressed, loop back
+       in al, 60h              ; reads the keyb that was pressed to reset the flag
+
+; re-enable all interrupts
+       sti
+
 .inf_loop:
        jmp .inf_loop
+
+; random number generator
+; by nuclear
+rand:
+       mov eax, [randval]
+       mul dword [randmul]
+       add eax, 12345
+       and eax, 0x7fffffff
+       mov [randval], eax
+       shr eax, 16
+       ret
+
+randmul dd 1103515245
+randval dd 0ace1h