podstawek

	org 	$8000
start:  ld 	a,%00010000	; load accumulator with any value that sets the 4th bit
	out	(&fe),a		; send that value to port 254, i.e. hexadecimal FE
	xor	%00010000	; flip the 4th bit to the opposite of what it was before
	out	(&fe),a		; send that value to port 254 again

	end start

podstawek

	org 	$8000
start:  ld 	a,%00010000
	ld	c,%00010000
	out	(&fe),a
	xor	c		; this is faster than xor %00010000
	out	(&fe),a
	end start

podstawek

; adapted from Pavel Lebedev (Мир звуков Спектрума, https://vtrd.in/book/ZXSWORLD.ZIP)
	org 	$8000
chord: 	ex	af,af'		; swap primary and alternative AF registers
	ld	b,d		; counter 2
	ld	c,e		; counter 1
beep:	ex	af,af'		; swap registers (swap the voice)
	dec	c		; decrement c
	jr	nz,cont		; if not zero, go to cont
	ld	c,e		; restore counter 1
	xor	16		; invert bit 4 of voice 1

podstawek

	org $8000
start: 	ld de, 500
flip: 	xor %00010111
	out (&fe), a
	ld bc, 500
freq: 	dec c
	jr nz, freq
	dec b
	jr nz, freq
	jr flip

podstawek

	org $8000
start:	di		; disables interrupts
flip:	xor %00010011
	out (&fe), a
	ld b, 100
freq:	dec b
	jr nz, freq
	jr flip
	ei		; re-enables interrupts
	end start

podstawek

// Define Arduino pin constants to correspond with MOS6522 pins
const byte CS1 = 24; // Chip Select 1
const byte CS2 = 23; // Chip Select 2
const byte RS0 = 38; // Register Select 0
const byte RS1 = 37; // Register Select 1
const byte RS2 = 36; // Register Select 2
const byte RS3 = 35; // Register Select 3
const byte RW  = 22; // Read-Write Line
const byte D0 =  33; // Data Bus 0
const byte D1 =  32; // Data Bus 1

podstawek

// Define Arduino pin constants to correspond with MOS6522 pins
const byte CS1 = 24; // Chip Select 1
const byte CS2 = 23; // Chip Select 2
const byte RS0 = 38; // Register Select 0
const byte RS1 = 37; // Register Select 1
const byte RS2 = 36; // Register Select 2
const byte RS3 = 35; // Register Select 3
const byte RW  = 22; // Read-Write Line
const byte D0 =  33; // Data Bus 0
const byte D1 =  32; // Data Bus 1

podstawek

const byte D0 = 44; // Digital Line 0
const byte D1 = 45; // Digital Line 1
const byte D2 = 46; // Digital Line 2

void setup() {
  pinMode(D0, OUTPUT);
  pinMode(D1, OUTPUT);
  pinMode(D2, OUTPUT);
}

podstawek

  // send a pattern to Shift Register (e.g. 01100101)
  digitalWrite(D7, LOW);
  digitalWrite(D6, HIGH);
  digitalWrite(D5, HIGH);
  digitalWrite(D4, LOW);
  digitalWrite(D3, LOW);
  digitalWrite(D2, HIGH);
  digitalWrite(D1, LOW);
  digitalWrite(D0, HIGH);

podstawek

void loop() {
  digitalWrite(D0, LOW);
  digitalWrite(D1, LOW);
  digitalWrite(D2, LOW);
  delay(2);
  digitalWrite(D0, LOW);
  digitalWrite(D1, LOW);
  digitalWrite(D2, HIGH);
  delay(2);
  ; (...end so on...)