Snippets
Created by
T McDonnell
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uses CRT, DOS;
{----------------(ASC Simulation)---------------}
{CPU Registers}
var
ACC : Longint; {ACCumulator}
MBR : Longint; {Memory Buffer Register}
MAR : Word; {Memory Address Register}
IR : Word; {Instruction Register}
PC : Word; {Program Counter}
IR1 : Word; {Index Register 1}
IR2 : Word; {Index Register 2}
IR3 : Word; {Index Register 3}
{Random Access Memory}
RAM : Array[1..1000] of Longint; {1Kb RAM}
{IR decoder variables}
memoryAddr : Integer; {IR bits 7-15} {0-511}
idx : Integer; {IR bits 0-1} {0-3}
indirect : Integer; {IT bit 2} {0-1}
opcode : Integer; {IR bits 3-6} {0-15}
{-----------------------------------------------}
{-----------------------------------------------}
var key : Char; {Stores users menu choice}
{-----------------------------------------------}
{-----------------------------------------------}
procedure PrintHex( X : Word);
const s : array[0..15] of char = '0123456789ABCDEF';
var i : integer;
begin
for i:=3 downto 0 do
Write( s[$000F and (X shr(i*4))]);
end;
{taken from PASCAL Programers Phasebook}
{by Ian A. Clari, Sigma Press, 1992}
{-----------------------------------------------}
procedure RegWin;
begin
Window(1,1,80,8);
TextBackground(blue);
TextColor(white);
ClrScr;
WriteLn('+============================================================================+');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
Write('+============================================================================+');
TextColor(yellow);
GotoXY(9,3); Write('ACCumalator:'); GotoXY(44,3); Write('Instruction Register:');
GotoXY(9,4); Write('Program Counter:'); GotoXY(44,4); Write('Index Register 1:');
GotoXY(9,5); Write('Memory Buffer Register:'); GotoXY(44,5); Write('Index Register 2:');
GotoXY(9,6); Write('Memory Address Register:'); GotoXY(44,6); Write('Index Register 3:');
TextColor(white);
GotoXY(34,3); PrintHex(ACC); GotoXY(66,3); PrintHex(IR);
GotoXY(34,4); PrintHex(PC); GotoXY(66,4); PrintHex(IR1);
GotoXY(34,5); PrintHex(MBR); GotoXY(66,5); PrintHex(IR2);
GotoXY(34,6); PrintHex(MAR); GotoXY(66,6); PrintHex(IR3);
end;
procedure MainWin;
begin
Window(1,9,80,25);
TextBackground(blue);
TextColor(white);
ClrScr;
WriteLn('+============================================================================+');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
Write('+============================================================================+');
TextColor(lightred);
GotoXY(11,16);
Write('A Simple Computer simulator - T.McDonnell, SYS-1C22,UEA,1999');
TextColor(yellow);
GotoXY(17,3); Write('1.....Load progam to ASC RAM');
GotoXY(17,4); Write('2.....Start ASC simulation using program in ASC RAM');
GotoXY(17,5); Write('3.....Step through a running ASC Simulation');
GotoXY(17,6); Write('4.....Show map of ASC RAM');
GotoXY(17,7); Write('5.....Edit contents of a ASC CPU register');
GotoXY(17,8); Write('6.....Edit contents of a ASC RAM address');
GotoXY(17,9); Write('7.....Set program break points');
GotoXY(17,11); Write('C.....Clear registers');
GotoXY(17,13); Write('X.....Exit ASC simulator');
end;
procedure Dialog;
begin
Window(21,12,60,18);
TextBackground(cyan);
TextColor(white);
WriteLn('+======================================+');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
Write('+======================================+');
TextColor(black);
end;
procedure Greeting;
begin
GotoXY(10,2); Write('A Simple Computer');
GotoXY(9,6); Write('T. McDonnell, 1999');
TextColor(lightred+blink);
GotoXY(10,4); Write('S I M U L A T O R');
repeat until KeyPressed;
end;
function Addr : Word;
var address : Word;
begin
CursorOn;
Dialog; GotoXY(6,4); Write('Address: ');
GotoXY(6,2); Write('Enter in either Hex or Dec');
GotoXY(6,6); Write('Use $ for Hex values');
GotoXY(15,4); TextBackground(lightgray); Write(' ');
GotoXY(15,4); TextColor(white); ReadLn(address);
CursorOff;
MainWin;
Addr := address;
end;
function Val : Word;
var value : Word;
begin
CursorOn;
Dialog; GotoXY(6,4); Write('Value: ');
GotoXY(6,2); Write('Enter in either Hex or Dec');
GotoXY(6,6); Write('Use $ for Hex values');
GotoXY(15,4); TextBackground(lightgray); Write(' ');
GotoXY(15,4); TextColor(white); ReadLn(value);
CursorOff;
MainWin;
Val := value;
end;
function UserIn : Word;
var data : Word;
begin
Window(21,1,60,7);
TextBackground(cyan);
TextColor(white);
WriteLn('+---------------------------------------------------------+');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
Write('+---------------------------------------------------------+');
TextColor(black);
Window(22,2,69,6);
GotoXY(3,3); Write('Enter Data: ');
TextBackground(lightgray); TextColor(white);
Write(' '); GotoXY(15,3);
ReadLn(data);
UserIn := data;
end;
procedure UserOut(data:Word);
begin
Window(21,1,60,7);
TextBackground(cyan);
TextColor(white);
WriteLn('+---------------------------------------------------------+');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
Write('+---------------------------------------------------------+');
TextColor(black);
Window(22,2,69,6);
WriteLn(data);
end;
procedure Fetch;
begin
memoryAddr := 0; idx := 0; indirect := 0; opcode := 0;
MAR := PC;
MBR := RAM[MAR];
PC := PC + 1;
IR := MBR;
end;
procedure Decode;
begin
memoryAddr := IR;
{--------------------------------------}
{calculate which index register, if any, is used}
if memoryAddr >= $0000 then
begin
idx := 3;
memoryAddr := memoryAddr - $0000;
end
else if memoryAddr >=$8000 then
begin
idx := 2;
memoryAddr := memoryAddr - $8000;
end
else if memoryAddr >=$4000 then
begin
idx := 1;
memoryAddr := memoryAddr - $8000;
end;
{--------------------------------------}
{check for indirect addressing mode}
if memoryAddr >= $2000 then
begin
indirect := 1;
memoryAddr := memoryAddr - $2000;
end;
{--------------------------------------}
{remove opcode}
if memoryAddr >= $1E00 then
begin
opcode := $F; {TDX I,x}
memoryAddr := memoryAddr - $1E00;
end
else if memoryAddr >= $1C00 then
begin
opcode := $E; {TIX I,x}
memoryAddr := memoryAddr - $1C00;
end
else if memoryAddr >= $1A00 then
begin
opcode := $D; {STX I,x}
memoryAddr := memoryAddr - $1A00;
end
else if memoryAddr >= $1800 then
begin
opcode := $C; {LDX, I,x}
memoryAddr := memoryAddr - $1800;
end
else if memoryAddr >= $1600 then
begin
opcode := $B; {SHR}
memoryAddr := memoryAddr - $1600;
end
else if memoryAddr >= $1400 then
begin
opcode := $A; {SHL}
memoryAddr := memoryAddr - $1400;
end
else if memoryAddr >= $1200 then
begin
opcode := $9; {WWD}
memoryAddr := memoryAddr - $1200;
end
else if memoryAddr >= $1000 then
begin
opcode := $8; {RWD}
memoryAddr := memoryAddr - $1000;
end
else if memoryAddr >= $0E00 then
begin
opcode := $7; {BIN x}
memoryAddr := memoryAddr - $0E00;
end
else if memoryAddr >= $0C00 then
begin
opcode := $6; {BIP x}
memoryAddr := memoryAddr - $0C00;
end
else if memoryAddr >= $0A00 then
begin
opcode := $5; {BRU x}
memoryAddr := memoryAddr - $0A00;
end
else if memoryAddr >= $0800 then
begin
opcode := $4; {HLT}
memoryAddr := memoryAddr - $0800;
end
else if memoryAddr >= $0600 then
begin
opcode := $3; {TCA}
memoryAddr := memoryAddr - $0600;
end
else if memoryAddr >= $0400 then
begin
opcode := $2; {ADD x}
memoryAddr := memoryAddr - $0400;
end
else if memoryAddr >= $0200 then
begin
opcode := $1; {STA x}
memoryAddr := memoryAddr - $0200;
end
else if memoryAddr >= $0000 then
begin
opcode := $0; {LDA x}
memoryAddr := memoryAddr - $0000;
end;
{------------------------------}
{update registers}
MAR := memoryAddr;
if idx = 0 then
begin
if indirect = 0 then
begin
MBR := RAM[MAR];
end
else
begin
MBR := RAM[MAR];
MAR := MBR;
MBR := RAM[MAR];
end;
end
else
begin
if indirect = 0 then
begin
if idx = 1 then MBR := RAM[MAR + IR1];
if idx = 2 then MBR := RAM[MAR + IR2];
if idx = 3 then MBR := RAM[MAR + IR3];
end
else
begin
if idx = 1 then MBR := RAM[MAR + IR1];
if idx = 2 then MBR := RAM[MAR + IR2];
if idx = 3 then MBR := RAM[MAR + IR3];
MAR := MBR;
MBR := RAM[MAR];
end;
end;
if opcode = $C then
begin
MAR := memoryAddr;
MBR := RAM[MAR];
end;
if opcode = $D then MAR := memoryAddr;
if opcode = $E then MAR := memoryAddr;
if opcode = $F then MAR := memoryAddr;
end;
procedure Execute;
begin
if opcode = $0 then ACC := MBR;
if opcode = $1 then
begin
MBR := ACC;
RAM[MAR] := MBR;
end;
if opcode = $2 then ACC := ACC + MBR;
if opcode = $3 then ACC := 0 - ACC;
if opcode = $5 then PC := MAR;
if opcode = $6 then if ACC > 0 then PC := MAR;
if opcode = $7 then if ACC < 0 then PC := MAR;
if opcode = $8 then ACC := UserIn;
if opcode = $9 then UserOut(ACC);
if opcode = $A then ACC := ACC * 2;
if opcode = $B then ACC := ACC DIV 2;
if opcode = $C then
begin
if idx = 1 then IR1 := MBR;
if idx = 2 then IR2 := MBR;
if idx = 3 then IR3 := MBR;
end;
if opcode = $D then
begin
if idx = 1 then MBR := IR1;
if idx = 2 then MBR := IR2;
if idx = 3 then MBR := IR3;
end;
if opcode = $E then
begin
if idx = 1 then
begin
IR1 := IR1 + 1;
if IR1 = 0 then PC := MAR;
end;
if idx = 2 then
begin
IR2 := IR2 + 1;
if IR2 = 0 then PC := MAR;
end;
if idx = 3 then
begin
IR3 := IR3 + 1;
if IR3 = 0 then PC := MAR;
end;
end;
if opcode = $F then
begin
if idx = 1 then
begin
IR1 := IR1 - 1;
if not(IR1 = 0) then PC := MAR;
end;
if idx = 2 then
begin
IR2 := IR2 - 1;
if not(IR2 = 0) then PC := MAR;
end;
if idx = 3 then
begin
IR3 := IR3 - 1;
if not(IR3 = 0) then PC := MAR;
end;
end;
end;
{---------------------------------------}
procedure Load;
var F : Text;
userfile : String;
address : integer;
temp : Word;
SRec : SearchRec;
begin
{--------------------}
Dialog;
GotoXY(3,2); Write('Load ASC machine code from...');
GotoXY(3,5); Write('Do not enter DOS extension (.asc)');
GotoXY(5,4); Write('File: ');
Textbackground(lightgray); TextColor(white); Write(' ');
CursorOn;
repeat
GotoXY(11,4); ReadLn(userfile);
until not(userfile='');
userfile := userfile + '.asc';
CursorOff; Dialog;
TextColor(lightred+blink); GotoXY(11,4); Write('Processing ',userfile);
{--------------------}
FindFirst(userfile, AnyFile, SRec);
if DosError = 2 then
begin
Dialog; GotoXY(6,4); TextColor(lightred);
Write('ERROR - File does not exist');
repeat until KeyPressed;
end
else
begin
{---------------------}
address := Addr;
Dialog;
TextColor(lightred+blink);
GotoXY(11,4); Write('Processing ',userfile);
{---------------------}
Assign(f,userfile); Reset(f);
repeat
if address > 1000 then
begin
Read(F, temp);
Dialog; GotoXY(6,4); TextColor(lightred);
Write('FATAL ERROR - ASC out of RAM');
repeat until KeyPressed;
end
else
begin
Read(F, RAM[address]);
address := address + 1;
end;
until Eof(F);
close(F);
end;
MainWin;
end;
procedure FetchExecute;
begin
PC := Addr;
Dialog; TextColor(lightred+blink);
GotoXY(11,4); Write('Processing...');
repeat
Fetch;
Decode;
Execute;
RegWin;
until opcode = $4;
MainWin;
end;
procedure Trace;
var
step : char;
charcheck : Integer;
begin
PC := Addr;
Dialog;
GotoXY(6,3); Write('[S] - Step');
GotoXY(6,5); Write('[X] - Exit');
repeat
charcheck := 0;
Fetch;
Decode;
Execute;
RegWin;
repeat
repeat until KeyPressed;
step := ReadKey;
if step = 'x' then
begin
step := 'X';
charcheck := 1;
end;
if step = 'X' then charcheck := 1;
if step = 's' then charcheck := 1;
if step = 'S' then charcheck := 1;
until charcheck = 1;
if opcode = $4 then step := 'X';
until step = 'X';
MainWin;
end;
procedure Map;
var
startAddr : Word;
endAddr : Word;
address : Word;
begin
Dialog; GotoXY(6,3); Write('Start Addr: ');
GotoXY(6,5); Write('End Addr: ');
GotoXY(6,2); Write('Enter in either Hex or Dec');
GotoXY(6,6); Write('Use $ for Hex values');
TextBackground(lightgray);
GotoXY(18,3); Write(' ');
GotoXY(18,5); Write(' ');
CursorOn; TextColor(white);
GotoXY(18,3); ReadLn(startAddr);
GotoXY(18,5); ReadLn(endAddr);
CursorOff;
MainWin;
{---------------------------}
Window(38,1,79,24);
WriteLn('+----------------------------------------------------------------------------+');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
WriteLn('| |');
Write('+----------------------------------------------------------------------------+');
TextColor(black);
GotoXY(4,2); Write('Address Contents');
GotoXY(19,3); Write('Hex Decimal');
{-------------------------------}
Window(43,5,74,22);
for address := startAddr to endAddr do
begin
TextColor(yellow); PrintHex(address);
TextColor(white); Write(' '); PrintHex(RAM[address]);
WriteLn(' ',RAM[address]);
end;
repeat until KeyPressed;
RegWin; MainWin;
end;
procedure RegEdit;
var
reg : String;
begin
Dialog;
GotoXY(3,2); Write('Enter Register code');
GotoXY(3,6); Write('Capital letters in register window');
GotoXY(6,4); Write('Register: ');
TextBackground(lightgray); TextColor(white);
GotoXY(16,4); Write(' ');
GotoXY(16,4); ReadLn(reg);
if reg='ACC' then ACC := Val;
if reg='acc' then ACC := Val;
if reg='PC' then PC := Val;
if reg='pc' then PC := Val;
if reg='MBR' then MBR := Val;
if reg='mbr' then MBR := Val;
if reg='MAR' then MAR := Val;
if reg='mar' then MAR := Val;
if reg='IR' then IR := Val;
if reg='ir' then IR := Val;
if reg='IR1' then IR1 := Val;
if reg='ir1' then IR1 := Val;
if reg='IR2' then IR2 := Val;
if reg='ir2' then IR2 := Val;
if reg='IR3' then IR3 := Val;
if reg='ir3' then IR3 := Val;
RegWin;
MainWin;
end;
procedure AddrEdit;
var
address : Word;
begin
address := Addr;
RAM[address] := Val;
end;
procedure BreakPts;
begin
end;
procedure Clear;
begin
ACC := 0; IR := 0;
PC := 0; IR1 := 0;
MAR := 0; IR2 := 0;
MBR := 0; IR3 := 0;
RegWin;
end;
{-------------------------------------------------}
{Main Subroutine}
begin
{startup}
CursorOff;
RegWin;
MainWin;
Dialog;
Greeting;
MainWin;
{main loop}
repeat
key := ReadKey;
case key of
'1' : Load;
'2' : FetchExecute;
'3' : Trace;
'4' : Map;
'5' : RegEdit;
'6' : AddrEdit;
'7' : BreakPts;
'C' : Clear;
'c' : Clear;
'x' : key := 'X';
end;
until key = 'X';
end
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