Added RAM2GS functionality

Makefile

@@ -1,14 +1,14 @@
 all:    RAM2Eutil.po RAM2Eutil.dbg.po
 
-.PHONY: clean
-
 obj:
 	@mkdir obj
 
 bin:
 	@mkdir bin
 
-ram2e.c:
+obj/main.o: obj main.c
+	cc65 main.c -O --cpu 6502 -t apple2enh -o obj/main.s
+	ca65 obj/main.s -o obj/main.o
 
 obj/ram2e.o: obj ram2e.c
 	cc65 ram2e.c -O --cpu 6502 -t apple2enh -o obj/ram2e.s
@@ -18,19 +18,35 @@ obj/ram2e.dbg.o: obj ram2e.c
 	cc65 ram2e.c -O --cpu 6502 -t apple2enh -o obj/ram2e.dbg.s -DSKIP_RAM2E_DETECT
 	ca65 obj/ram2e.dbg.s -o obj/ram2e.dbg.o
 
-bin/ram2e.sys: bin obj/ram2e.o
-	ld65 -o bin/ram2e.sys obj/ram2e.o -C apple2enh-system.cfg --lib apple2enh.lib -D __EXEHDR__=0
+obj/ram2gs_asm.o: obj ram2gs_asm.s
+	ca65 ram2gs_asm.s -o obj/ram2gs_asm.o
 
-bin/ram2e.dbg.sys: bin obj/ram2e.dbg.o
-	ld65 -o bin/ram2e.dbg.sys obj/ram2e.dbg.o -C apple2enh-system.cfg --lib apple2enh.lib -D __EXEHDR__=0
+obj/ram2gs.o: obj ram2gs.c
+	cc65 ram2gs.c -O --cpu 6502 -t apple2enh -o obj/ram2gs.s
+	ca65 obj/ram2gs.s -o obj/ram2gs.o
 
-RAM2Eutil.po: bin/ram2e.sys
+obj/ram2gs.dbg.o: obj ram2gs.c
+	cc65 ram2gs.c -O --cpu 6502 -t apple2enh -o obj/ram2gs.dbg.s -DSKIP_RAM2GS_DETECT
+	ca65 obj/ram2gs.dbg.s -o obj/ram2gs.dbg.o
+
+obj/util.o: obj util.c
+	cc65 util.c -O --cpu 6502 -t apple2enh -o obj/util.s
+	ca65 obj/util.s -o obj/util.o
+
+bin/main.sys: bin obj/main.o obj/ram2e.o obj/ram2gs.o obj/ram2gs_asm.o obj/util.o
+	ld65 -o bin/main.sys obj/main.o obj/ram2gs.o obj/ram2e.o obj/ram2gs_asm.o obj/util.o -C apple2enh-system.cfg --lib apple2enh.lib -D __EXEHDR__=0
+
+bin/main.dbg.sys: bin obj/main.o obj/ram2e.dbg.o obj/ram2gs.dbg.o obj/ram2gs_asm.o obj/util.o
+	ld65 -o bin/main.dbg.sys obj/main.o obj/ram2gs.dbg.o obj/ram2e.dbg.o obj/ram2gs_asm.o obj/util.o -C apple2enh-system.cfg --lib apple2enh.lib -D __EXEHDR__=0
+
+RAM2Eutil.po: bin/main.sys
 	cp prodos140.po bin/RAM2Eutil.po
-	cat bin/ram2e.sys | java -jar ./AppleCommander-ac-1.6.0.jar -p bin/RAM2Eutil.po ram2e.system sys 0x2000
+	cat bin/main.sys | java -jar ./AppleCommander-ac-1.6.0.jar -p bin/RAM2Eutil.po gwram.system sys 0x2000
 
-RAM2Eutil.dbg.po: bin/ram2e.dbg.sys
+RAM2Eutil.dbg.po: bin/main.dbg.sys
 	cp prodos140.po bin/RAM2Eutil.dbg.po
-	cat bin/ram2e.dbg.sys | java -jar ./AppleCommander-ac-1.6.0.jar -p bin/RAM2Eutil.dbg.po ram2e.system sys 0x2000
+	cat bin/main.dbg.sys | java -jar ./AppleCommander-ac-1.6.0.jar -p bin/RAM2Eutil.dbg.po gwram.system sys 0x2000
 
+.PHONY: clean
 clean:
 	rm -fr bin obj

main.c

@@ -0,0 +1,32 @@
+#include <conio.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "ram2e.h"
+#include "ram2gs.h"
+
+int main(void)
+{
+	// First clear screen
+	clrscr();
+
+	// Check machine type
+	switch ((get_ostype() & 0xF0)) {
+		case APPLE_IIE:
+			ram2e_main();
+			break;
+		case APPLE_IIGS:
+			ram2gs_main();
+			break;
+		default:
+			// If not on IIe or IIgs, show an error message and quit
+			gotoxy(0, 8);
+			cputs(" THIS PROGRAM REQUIRES APPLE IIE OR IIGS");
+			gotoxy(0, 10);
+			cputs(" PRESS ANY KEY TO QUIT.");
+			cgetc(); // Wait for key
+			clrscr(); // Clear screen before quitting
+			return EXIT_SUCCESS;
+			break;
+	} 
+}

ram2e.c

@@ -5,20 +5,10 @@
 #include <ctype.h>
 #include <stdint.h>
 
-#define true 1
-#define false 0
+#include "util.h"
 
-
-#define VBL ((signed char*)0xC019)
-const uint8_t SPIN_HALFCYCLES = 3;
-const uint8_t SPIN_FRAMESPERCHAR = 4;
-
-#define PB0 ((char*)0xC061)
-#define PB1 ((char*)0xC062)
-static char read_applekey(void) { return (*PB0 | *PB1) & 0x80; }
-
-char _cmd;
-char _arg;
+static char _cmd;
+static char _arg;
 /* ram2e_cmd(...) issues a coded command+argument sequence to the RAM2E */
 static void ram2e_cmd(char cmd, char arg) {
 	// Load operation and data bytes into X and Y registers
@@ -100,7 +90,7 @@ static char auxram_detect() {
 }
 
 /* ram2e_detect() returns true if a RAM2E II has been detected */
-uint8_t _detect;
+static uint8_t _detect;
 static char ram2e_detect() {
 	#ifdef SKIP_RAM2E_DETECT
 	return true;
@@ -148,8 +138,8 @@ static char ram2e_detect() {
 }
 
 /* ramworks_getsize() returns the number of banks of RAM2E aux memory */
-uint8_t _rwsize;
-uint8_t _rwnot16mb;
+static uint8_t _rwsize;
+static uint8_t _rwnot16mb;
 static uint16_t ramworks_getsize() {
 	_rwnot16mb = 1; // Set "not 16 mb" flag
 
@@ -169,11 +159,11 @@ static uint16_t ramworks_getsize() {
 	CountLoop:
 	__asm__("sty $C073"); // Set bank
 	__asm__("cpy $00"); // Is bank num stored at address 0?
-	__asm__("bne %g", NotMem); // If not, skip increment
+	__asm__("bne %g", AfterInc); // If not, skip increment
 	__asm__("inx"); // If so, increment bank count
-	__asm__("bne %g", NotMem); // Skip next if x!=0
+	__asm__("bne %g", AfterInc); // Skip next if x!=0
 	__asm__("stx %v", _rwnot16mb); // Othwerwise rolled over so clear rwnot16mb
-	NotMem:
+	AfterInc:
 	__asm__("iny"); // Move to next bank
 	__asm__("bne %g", CountLoop); // Repeat if not on bank 0
 
@@ -250,67 +240,12 @@ static void menu(void)
 	cputs("Press [Q] to quit without saving.");
 }
 
-static void spin(uint8_t x, uint8_t y) { 
-	char i;
-
-	// Sync to frame before starting
-	while (*VBL >= 0);
-
-	// Wait and animate spinner.
-	// Spin_half
-	for (i = 0; i < SPIN_HALFCYCLES; i++) {
-		char j;
-		for (j = 0; j < 4; j++) {
-			char spinchar;
-			char k;
-
-			// Assign spinner char based on j
-			switch (j) {
-				case 0: spinchar = '\\'; break;
-				case 1: spinchar = '|'; break;
-				case 2: spinchar = '/'; break;
-				case 3: spinchar = '-'; break;
-				default: spinchar = '-'; break;
-			}
-
-			// Write it to screen
-			gotoxy(x, y);
-			putchar(spinchar);
-
-			// Wait specificed number of frames
-			for (k = 0; k < SPIN_FRAMESPERCHAR; k++) {
-				while (*VBL < 0);
-				while (*VBL >= 0);
-			}
-		}
-	}
-
-	// Wait a frame when finished
-	while (*VBL < 0);
-	while (*VBL >= 0);
-}
-
-int main(void)
+int ram2e_main(void)
 {
 	char mask;
 	char nvm;
 	int reset_count;
 
-	// First clear screen
-	clrscr();
-
-	// Make sure we are running on an Apple IIe
-	if((get_ostype() & 0xF0) != APPLE_IIE) {
-		// If not on Apple IIe, show an error message and quit
-		gotoxy(0, 8);
-		cputs(" THIS PROGRAM REQUIRES AN APPLE IIE.");
-		gotoxy(0, 10);
-		cputs(" PRESS ANY KEY TO QUIT.");
-		cgetc(); // Wait for key
-		clrscr(); // Clear screen before quitting
-		return EXIT_SUCCESS;
-	}
-
 	// Check for RAM2E
 	if(!auxram_detect() || !ram2e_detect()) {
 		// If no RAM2E, show an error message and quit
@@ -331,7 +266,7 @@ int main(void)
 	reset_count = 0;
 	while (true) {
 		// Set capacity mask or quit according to keypress.
-		switch (toupper(cgetc())) {
+		switch (toupper(cgetc() & 0x7F)) {
 			case 'Q' : {
 				clrscr();
 				return EXIT_SUCCESS;
@@ -366,8 +301,7 @@ int main(void)
 			} default: continue;
 		}
 
-		// Check if pressed with apple key.
-		// If so, save to nonvolatile memory.
+		// Check if pressed with apple key. If so, save to nonvolatile memory.
 		if (read_applekey()) { nvm = true; }
 		break;
 	}

ram2e.h

@@ -0,0 +1,6 @@
+#ifndef RAM2E_H
+#define RAM2E_H
+
+int ram2e_main(void);
+
+#endif /* RAM2E_H */

ram2gs.c

@@ -0,0 +1,173 @@
+#include <stdlib.h>
+#include <conio.h>
+#include <string.h>
+#include <stdio.h>
+#include <ctype.h>
+#include <stdint.h>
+
+#include "util.h"
+#include "ram2gs_asm.h"
+
+static void ram2gs_erase() { ram2gs_cmd(0x28); }
+static void ram2gs_program() { ram2gs_cmd(0x24); }
+static void ram2gs_set4mb() { ram2gs_cmd(0x10); }
+static void ram2gs_set8mb() { ram2gs_cmd(0x11); }
+static void ram2gs_setnvm(char en8meg) {
+	char i;
+	// Clock in 0 to enable this setting entry
+	ram2gs_cmd(0x20);
+	ram2gs_cmd(0x22);
+
+	if (en8meg) {
+		// Clock in 1 to enable 8mb
+		ram2gs_cmd(0x21);
+		ram2gs_cmd(0x23);
+	} else {
+		// Clock in 0 to disable 8mb
+		ram2gs_cmd(0x20);
+		ram2gs_cmd(0x22);
+	}
+
+	// Clock in 14 dummy "1"s
+	for (i = 0; i < 14; i++) {
+		ram2gs_cmd(0x21);
+		ram2gs_cmd(0x23);
+	}
+
+	ram2gs_program();
+}
+
+static void menu(void)
+{
+	uint8_t bankcount = ram2gs_getsize();
+	gotoxy(5, 1);
+	cputs("-- RAM2GS Capacity Settings --");
+	gotoxy(4, 3);
+	printf("Current RAM2GS capacity: %d kB", bankcount * 64);
+
+	gotoxy(1, 6);
+	cputs("Select desired memory capacity:");
+
+	gotoxy(4, 8);
+	cputs("1. 4 megabytes");
+	gotoxy(4, 10);
+	cputs("2. 8 megabytes");
+
+	gotoxy(1, 18);
+	cputs("Capacity will be saved until power-off.");
+
+	gotoxy(1, 20);
+	cputs("To remember capacity setting in");
+	gotoxy(1, 21);
+	cputs("nonvolatile memory, press Apple+number.");
+
+	gotoxy(1, 23);
+	cputs("Press [Q] to quit without saving.");
+}
+
+int ram2gs_main(void)
+{
+	char en8meg;
+	char nvm;
+	int reset_count;
+
+	// Check for RAM2GS
+	#ifndef SKIP_RAM2GS_DETECT
+	if(!ram2gs_detect()) {
+		// If no RAM2GS, show an error message and quit
+		gotoxy(0, 8);
+		cputs(" No RAM2GS II detected.");
+		gotoxy(0, 10);
+		cputs(" Press any key to quit.");
+		cgetc(); // Wait for key
+		clrscr(); // Clear screen before quitting
+		return EXIT_SUCCESS;
+	}
+	#endif
+
+	menu(); // Print menu
+
+	// Get user choice from menu
+	en8meg = 0;
+	nvm = 0;
+	reset_count = 0;
+	while (true) {
+		// Set capacity or quit according to keypress.
+		switch (toupper(cgetc() & 0x7F)) {
+			case 'Q' : {
+				clrscr();
+				return EXIT_SUCCESS;
+			}
+			case '!': nvm = true;
+			case '1': en8meg = 0; ram2gs_set4mb(); break;
+			case '@': nvm = true;
+			case '2': en8meg = 1; ram2gs_set8mb(); break;
+			case 'R': {
+				reset_count++;
+				if (reset_count >= 100) {
+					// Show message about saving.
+					clrscr(); // Clear screen
+					gotoxy(1, 8);
+					cputs("Resetting RAM2GS settings.");
+					gotoxy(1, 9);
+					cputs("Do not turn off your Apple.");
+
+					ram2gs_erase(); // Erase RAM2GS settings memory
+					ram2gs_set8mb(); // Enable 8 megabytes now
+
+					// Wait for >= 500ms on even the fastest systems.
+					spin(32, 8);
+					
+					// Show success message and quit
+					clrscr(); // Clear screen
+					gotoxy(1, 8);
+					cputs("RAM2GS settings reset successfully.");
+					goto end;
+				}
+			} default: continue;
+		}
+
+		// Check if pressed with apple key. If so, save to nonvolatile memory.
+		if (read_applekey()) { nvm = true; }
+		break;
+	}
+
+	// Clear screen in preparation to show saving or success message.
+	clrscr();
+
+	if (nvm) { // Save in NVM if requested.
+		// Show message about saving.
+		gotoxy(1, 8);
+		cputs("Saving RAM2GS capacity setting.");
+		gotoxy(1, 9);
+		cputs("Do not turn off your Apple.");
+		// Save capacity in nonvolatile memory.
+		ram2gs_setnvm(en8meg);
+		// Wait for >= 500ms on even the fastest systems.
+		spin(33, 8);
+		// Print success message
+		clrscr(); // Clear screen
+		gotoxy(1, 8);
+		cputs("RAM2GS capacity saved successfully.");
+	} else { // Print success message if not saving in NVM.
+		gotoxy(1, 8);
+		cputs("RAM2GS capacity set successfully.");
+	}
+
+	end:
+	if (nvm) { // Show end message for nonvolatile save
+		gotoxy(1, 10);
+		cputs("You may now turn off your Apple.");
+		gotoxy(1, 12);
+		cputs("You may also reset your Apple for");
+		gotoxy(1, 13);
+		cputs("the setting change to take effect.");
+	} else { // Show end message for volatile save
+		gotoxy(1, 10);
+		cputs("Please reset your Apple for");
+		gotoxy(1, 11);
+		cputs("the setting change to take effect.");
+	}
+	// Don't quit. Instead leave prompt asking user to reset.
+	while(1) { cgetc(); }
+}

ram2gs.h

@@ -0,0 +1,6 @@
+#ifndef RAM2GS_H
+#define RAM2GS_H
+
+int ram2gs_main(void);
+
+#endif /* RAM2GS_H */

ram2gs_asm.h

@@ -0,0 +1,8 @@
+#ifndef RAM2GS_ASM_H
+#define RAM2GS_ASM_H
+
+uint8_t __fastcall__ ram2gs_getsize(void);
+uint8_t __fastcall__ ram2gs_detect(void);
+uint8_t __fastcall__ ram2gs_cmd(char cmd);
+
+#endif /* RAM2GS_ASM_H */

ram2gs_asm.s

@@ -0,0 +1,306 @@
+.setcpu		"65816"
+.autoimport on
+.importzp	sp
+
+.export 	_ram2gs_getsize
+.export 	_ram2gs_detect
+.export 	_ram2gs_cmd
+
+.macro A8
+       sep #$20 ; put the 65C816 in 8-bit accumulator mode
+      .A8
+.endmacro
+
+.macro I8
+       sep #$10 ; put the 65C816 in 8-bit index register mode
+      .I8
+.endmacro
+
+.macro AI8
+       sep #$30 ; put the 65C816 in 8-bit accumulator and index register mode
+      .A8
+      .I8
+.endmacro
+
+.macro A16
+       rep #$20 ; put the 65C816 in 8-bit accumulator mode
+      .A16
+.endmacro
+
+.macro I16
+       rep #$10 ; put the 65C816 in 8-bit index register mode
+      .I16
+.endmacro
+
+.macro AI16
+       rep #$30 ; put the 65C816 in 8-bit accumulator and index register mode
+      .A16
+      .I16
+.endmacro
+
+.segment	"CODE"
+
+.proc _gsram_getsize: near
+.A8
+.I8
+	; Preamble
+	sei				; Disable interrupts
+	clc				; Clear carry
+	xce				; Clear emulation bit
+	php				; Push status
+	phb				; Push bank
+	AI8
+
+	; Store bank number at address 0xFFFF in each bank
+	ldy #$7F		; Start at bank 0x7F
+	BankSetLoop:
+	phy				; Push future bank
+	plb 			; Pull bank
+	lda $8000		; Get address 0xFFFF in this bank
+	pha				; Save old address 0xFFFF contents
+	tya				; A = Y
+	eor #$FF		; Flip all bits
+	tay				; Y = A
+	sty $8000		; Overwrite address 0xFFFF with bank number
+	eor #$FF		; Flip all bits back
+	tay				; Y = A
+	dey				; Decrement bank number
+	cpy #$FF		; Have we wrapped around?
+	bne BankSetLoop ; If not, repeat
+
+	; Count banks with matching bank number
+	ldy #$00		; Y is bank
+	ldx #$00		; X is count
+	CountLoop:
+	phy				; Push future bank
+	plb				; Pull bank
+	tya				; A = Y
+	eor #$FF		; Flip all bits
+	tay				; Y = A
+	cpy $8000		; Is bank num stored at address 0xFFFF?
+	bne AfterInc	; If not, skip increment
+	inx				; If so, increment bank count
+	AfterInc:
+	eor #$FF		; Flip all bits back
+	tay				; Y = A
+	pla				; Get contents to restore
+	sta $8000		; Restore address 0xFFFF in this bank
+	iny				; Move to next bank
+	cpy #$80		; Are we at bank 0x80 yet?
+	bne CountLoop	; If not, repeat
+
+	; Postamble
+	plb				; Restore bank
+	plp				; Restore status
+	xce				; Restore emulation bit
+	cli				; Enable interrupts
+	txa				; Transfer bank count to A
+	rts
+.endproc
+
+.proc _ram2gs_getsize: near
+.A8
+.I8
+	; Preamble
+	sei				; Disable interrupts
+	clc				; Clear carry
+	xce				; Clear emulation bit
+	php				; Push status
+	phb				; Push bank
+	AI8
+
+	; Go to bank 3F
+	ldy #$3F
+	phy
+	plb
+	; Save 3F/3456
+	ldx $3456
+
+	; Go to bank 7F
+	ldy #$7F
+	phy
+	plb
+	; Invert 7F/3456
+	lda $3456
+	eor #$FF
+	sta $3456
+
+	; Go to bank 3F
+	ldy #$3F
+	phy
+	plb
+	; Has 3F/3456 changed?
+	cpx $3456
+	php
+
+	; Go to bank 7F
+	ldy #$7F
+	phy
+	plb
+	; Restore 7F/3456
+	eor #$FF
+	sta $3456
+
+	; Check result
+	ldx #$80
+	plp
+	beq _ram2gs_getsize_return
+	ldx #$40
+
+	; Postamble
+	_ram2gs_getsize_return:
+	plb				; Restore bank
+	plp				; Restore status
+	xce				; Restore emulation bit
+	cli				; Enable interrupts
+	txa				; Transfer bank count to A
+	rts
+.endproc
+
+
+.proc _unswap: near
+.A8
+.I8
+	; Save current bank and accumulator
+	phb
+	pha
+	; Switch to bank 0xFB
+	lda #$FB
+	pha
+	plb
+	; Submit C1AD
+	lda #$C1
+	sta $FFFE
+	lda #$AD
+	sta $FFFF
+	; Pull and submit command 
+	lda #$00
+	sta $FFFD
+	; Restore accumulator and bank and return
+	pla
+	plb
+	rts
+.endproc
+
+.proc _swap: near
+.A8
+.I8
+	; Save current bank and accumulator
+	phb
+	pha
+	; Switch to bank 0xFB
+	lda #$FB
+	pha
+	plb
+	; Submit C1AD
+	lda #$C1
+	sta $FFFE
+	lda #$AD
+	sta $FFFF
+	; Pull and submit command 
+	lda #$01
+	sta $FFFD
+	; Restore accumulator and bank and return
+	pla
+	plb
+	rts
+.endproc
+
+.proc _ram2gs_detect: near
+.A8
+.I8
+	; Preamble
+	sei				; Disable interrupts
+	clc				; Clear carry
+	xce				; Clear emulation bit
+	php				; Push status
+	phb				; Push bank
+	AI8
+
+	; Switch to bank 0x3F
+	lda #$3F
+	pha
+	plb
+
+	; Unswap
+	jsr _unswap
+	; Save unswapped 3F/8000
+	lda $8000
+	pha
+	; Swap
+	jsr _swap
+	; Save swapped 3F/8000
+	lda $8000
+	pha
+
+	; Store 0xFF in swapped
+	lda #$FF
+	sta $8000
+	; Verify 0xFF stored
+	lda $8000
+	cmp #$FF
+	bne _ram2gs_detect_fail
+
+	; Unswap
+	jsr _unswap
+	; Store 0x00 in unswapped
+	lda #$00
+	sta $8000
+	; Verify 0x00 stored
+	lda $8000
+	cmp #$00
+	bne _ram2gs_detect_fail
+
+	; Swap
+	jsr _swap
+	; Verify 0xFF stored
+	lda $8000
+	cmp #$FF
+	bne _ram2gs_detect_fail
+
+	; Get success return value and jump to postamble
+	ldx #$01		; Get success falue
+	bne _ram2gs_detect_return ; Jump to postamble
+
+	; Fail
+	_ram2gs_detect_fail:
+	ldx #$00		; Get fail value
+
+	; Postamble
+	_ram2gs_detect_return:
+	jsr _swap		; Swap
+	pla				; Get value to restore to swapped bank 3F
+	sta $8000		; Restore
+	jsr _unswap		; Unswap
+	pla				; Get value to restore to unswapped bank 3F
+	sta $8000		; Restore
+	txa				; Put return value in accumulator
+	plb				; Restore bank
+	plp				; Restore status
+	xce				; Restore emulation bit
+	cli				; Enable interrupts
+	rts
+.endproc
+
+.proc _ram2gs_cmd: near
+.A8
+.I8
+	; Save current bank and command in accumulator
+	phb
+	pha
+	; Switch to bank 0xFB
+	lda #$FB
+	pha
+	plb
+	; Submit C1AD
+	lda #$C1
+	sta $FFFE
+	lda #$AD
+	sta $FFFF
+	; Pull and submit command 
+	pla
+	sta $FFFD
+	; Restore bank and return
+	plb
+	rts
+.endproc

util.c

@@ -0,0 +1,52 @@
+#include "util.h"
+
+#include <stdint.h>
+#include <stdio.h>
+#include <conio.h>
+
+#define PB0 ((char*)0xC061)
+#define PB1 ((char*)0xC062)
+char read_applekey(void) { return ((*PB0) | (*PB1)) & 0x80; }
+
+#define VBL ((signed char*)0xC019)
+#define SPIN_HALFCYCLES 3
+#define SPIN_FRAMESPERCHAR 4
+void spin(uint8_t x, uint8_t y) { 
+	char i;
+
+	// Sync to frame before starting
+	while (*VBL >= 0);
+
+	// Wait and animate spinner.
+	// Spin_half
+	for (i = 0; i < SPIN_HALFCYCLES; i++) {
+		char j;
+		for (j = 0; j < 4; j++) {
+			char spinchar;
+			char k;
+
+			// Assign spinner char based on j
+			switch (j) {
+				case 0: spinchar = '\\'; break;
+				case 1: spinchar = '|'; break;
+				case 2: spinchar = '/'; break;
+				case 3: spinchar = '-'; break;
+				default: spinchar = '-'; break;
+			}
+
+			// Write it to screen
+			gotoxy(x, y);
+			putchar(spinchar);
+
+			// Wait specificed number of frames
+			for (k = 0; k < SPIN_FRAMESPERCHAR; k++) {
+				while (*VBL < 0);
+				while (*VBL >= 0);
+			}
+		}
+	}
+
+	// Wait a frame when finished
+	while (*VBL < 0);
+	while (*VBL >= 0);
+}

util.h

@@ -0,0 +1,12 @@
+#include <stdint.h>
+
+#ifndef UTIL_H
+#define UTIL_H
+
+#define true 1
+#define false 0
+
+char read_applekey(void);
+void spin(uint8_t x, uint8_t y);
+
+#endif /* UTIL_H */