uk.co.javagear
Class Z80

java.lang.Object
  uk.co.javagear.Z80

public final class Z80
extends java.lang.Object

Zilog Z80 CPU Emulation.
For generic Z80 use the following need to be implemented correctly:

• + Interrupt Modes 0 and 2
• + Certain undocumented opcodes
• + Make stack pointer wrap properly

Version:

18th January 2003

Author:

Copyright (C) 2002-2003 Chris White

See Also:

"JavaGear Final Project Report"

Field Summary

private Accumulator	a Accumulator.
private Registers	bc Loop counter.
private int[]	daa Pre-calculated result for DAA instruction.
private Registers	de General purpose.
private boolean	EI_inst Previous instruction was EI.
private Flag	f Flag register.
private boolean	halt Halt instruction.
private Registers	hl General purpose.
private int	i Interrupt page address register.
private boolean	iff1 Interrupt flip-flop 1.
private boolean	iff2 Interrupt flip-flop 2.
private int	im Interrupt Mode (0,1,2).
private InterruptLine	irq Pointer to Z80 interrupt line.
private Registers	ix Index page address register.
private Registers	iy Index page address register.
private Memory	mem Pointer to system memory.
private short[]	opcbstates
private short[]	opddstates
private short[]	opedstates
private short[]	opindexcbstates
private short[]	opstates
private int	pc Program counter.
private Ports	port Pointer to Z80 ports.
private Refresh	r Memory refresh register.
private int	sp Stack pointer.
private int	tstates T states.

Constructor Summary

Z80(Memory m, Ports p, InterruptLine i)
Z80 Constructor.

Method Summary

private void	bit(int value, int b) CB BIT - Test Bit.
private void	call(boolean condition) Call.
private void	ccf() CCF - Complement Carry Flag.
private void	consoledebug() Output contents of Z80 registers to console for debugging purposes.
private int	d() Get Offset Value from memory for index operations.
private void	daa() DAA - Decimal Adjust Accumulator adds 6 to left and/or right nibble.
boolean	debug(int cycles) Run Z80 for a single instruction (debugging purposes).
private void	dechl(int offset) DEC (HL) - Decrement memory location.
private void	doCB(int opcode) Execute CB prefixed opcode.
void	doED(int opcode) Execute ED Prefixed Opcode.
private void	doIndexCB(Registers index) Execute DDCB/FDCB Prefixed Opcode.
private void	doIndexOp(int opcode, Registers index) Execute DD/FD Prefixed Index Opcode.
private void	doOp(int opcode) Execute opcode.
void	exall() Exchange registers with shadow registers.
private void	generateDAATable() Pre-calculate DAA Table.
int	getA() Get value of accumulator.
int	getB() Get value of B register.
boolean	getBit3() Get state of bit 3 flag.
boolean	getBit5() Get state of bit 5 flag.
int	getC() Get value of C register.
boolean	getCarry() Get state of the carry flag.
int	getD() Get value of D register.
int	getE() Get value of E register.
int	getF() Get value of flag register.
int	getH() Get value of H register.
boolean	getHc() Get state of halfcarry flag.
int	getIX() Get value of IX register.
int	getIY() Get value of IY register.
int	getL() Get value of L register.
java.lang.String	getMnu() Return mnemonic of next opcode for debugging purposes.
boolean	getNegative() Get State of Negative Flag.
java.lang.String	getOp() Return next opcode for debugging purposes.
boolean	getParity() Get state of parity flag.
int	getPC() Get value of the program counter.
int	getR() Get value of the Refresh register.
boolean	getSign() Get state of sign flag.
int	getSP() Get value of the stack pointer.
boolean	getZero() Get state of zero flag.
private void	inchl(int offset) INC (HL) - increment memory location.
void	interrupt() Normal interrupt routine.
private void	jp(boolean condition) Jump.
private void	jr(boolean condition) Jump relative.
void	nmi() Generate Non Maskable Interrupt (NMI).
private int	pop() Pop value off stack.
private void	push(int value) Push value onto stack.
private int	res(int value, int b) CB RES - Reset Bit.
void	reset() Reset Z80.
private void	ret(boolean condition) Return.
private int	rl(int value) CB RL - Rotate Left.
private int	rlc(int value) CB RLC - Rotate Left Carry.
private int	rr(int value) CB RR - Rotate Right.
private int	rrc(int value) CB RRC - Rotate Right Carry.
void	run(int cycles) Run Z80.
void	setA(int reg) Set accumulator.
void	setBC(int reg) Set BC register pair.
private int	setBit(int value, int b) CB SET - Set Bit On.
void	setDE(int reg) Set DE register pair.
void	setF(int reg) Set flag register.
void	setHL(int reg) Set HL register pair.
void	setI(int reg) Set interrupt register.
void	setIFF2(boolean flag) Set interrupt flip-flop 2.
void	setIM(int mode) Set interrupt mode.
void	setIX(int reg) Set IX register pair.
void	setIY(int reg) Set IY register pair.
void	setR(int reg) Set refresh register.
void	setSP(int value) Set stack pointer.
private int	sla(int value) CB SLA - Shift Left Arithmetic.
private int	sll(int value) CB SLL - Logical Left Shift.
private int	sra(int value) CB SRA - Shift Right Arithmetic.
private int	srl(int value) CB SRL - Logical Shift Right.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

pc

private int pc

Program counter.

sp

private int sp

Stack pointer.

im

private int im

Interrupt Mode (0,1,2).

iff1

private boolean iff1

Interrupt flip-flop 1.

iff2

private boolean iff2

Interrupt flip-flop 2.

halt

private boolean halt

Halt instruction.

EI_inst

private boolean EI_inst

Previous instruction was EI.

irq

private InterruptLine irq

Pointer to Z80 interrupt line.

mem

private Memory mem

Pointer to system memory.

port

private Ports port

Pointer to Z80 ports.

f

private Flag f

Flag register.

a

private Accumulator a

Accumulator.

bc

private Registers bc

Loop counter.

de

private Registers de

General purpose.

hl

private Registers hl

General purpose.

ix

private Registers ix

Index page address register.

iy

private Registers iy

Index page address register.

r

private Refresh r

Memory refresh register.

i

private int i

Interrupt page address register.

daa

private int[] daa

Pre-calculated result for DAA instruction.

tstates

private int tstates

T states.

opstates

private final short[] opstates

opcbstates

private final short[] opcbstates

opddstates

private final short[] opddstates

opindexcbstates

private final short[] opindexcbstates

opedstates

private final short[] opedstates

Constructor Detail

Z80

public Z80(Memory m,
           Ports p,
           InterruptLine i)

Z80 Constructor.

Parameters:

m - pointer to system memory.

p - pointer to Z80's ports.

i - pointer to Z80's interrupt line.

Method Detail

reset

public void reset()

Reset Z80. Note that some of these values aren't what a real Z80 would reset to. They are the values that the SMS BIOS (to the best of my knowledge) sets the registers to. For example, the Index Registers should reset to 0xFFFF but doing so breaks 'Prince of Persia', so they are set to 0x0000. The stack pointer is also reset to 0xDFF0 as opposed to 0x0000.

setA

public void setA(int reg)

Set accumulator.

Parameters:

reg - value to set register with

setF

public void setF(int reg)

Set flag register.

Parameters:

reg - value to set register with.

setI

public void setI(int reg)

Set interrupt register.

Parameters:

reg - value to set register with.

setR

public void setR(int reg)

Set refresh register.

Parameters:

reg - value to set register with.

setBC

public void setBC(int reg)

Set BC register pair.

Parameters:

reg - value to set register with.

setDE

public void setDE(int reg)

Set DE register pair.

Parameters:

reg - value to set register with.

setHL

public void setHL(int reg)

Set HL register pair.

Parameters:

reg - value to set register with.

setIX

public void setIX(int reg)

Set IX register pair.

Parameters:

reg - value to set register with.

setIY

public void setIY(int reg)

Set IY register pair.

Parameters:

reg - value to set register with.

setSP

public void setSP(int value)

Set stack pointer.

Parameters:

value - value to set stack pointer with

setIM

public void setIM(int mode)

Set interrupt mode.

Parameters:

mode - interrupt mode 0 - 2.

setIFF2

public void setIFF2(boolean flag)

Set interrupt flip-flop 2.

Parameters:

flag - true is On, false is Off.

exall

public void exall()

Exchange registers with shadow registers.

getA

public int getA()

Get value of accumulator.

Returns:

value stored in accumulator.

getF

public int getF()

Get value of flag register.

Returns:

value stored in flag register.

getB

public int getB()

Get value of B register.

Returns:

value stored in B register.

getC

public int getC()

Get value of C register.

Returns:

value stored in C register.

getD

public int getD()

Get value of D register.

Returns:

value stored in D register.

getE

public int getE()

Get value of E register.

Returns:

value stored in E register.

getH

public int getH()

Get value of H register.

Returns:

value stored in H register.

getL

public int getL()

Get value of L register.

Returns:

value stored in L register.

getR

public int getR()

Get value of the Refresh register.

Returns:

value stored in the Refresh register.

getIX

public int getIX()

Get value of IX register.

Returns:

value stored in IX register.

getIY

public int getIY()

Get value of IY register.

Returns:

value stored in IY register.

getPC

public int getPC()

Get value of the program counter.

Returns:

value stored in the program counter.

getSP

public int getSP()

Get value of the stack pointer.

Returns:

value stored in the stack pointer.

getCarry

public boolean getCarry()

Get state of the carry flag.

Returns:

true if set.

getNegative

public boolean getNegative()

Get State of Negative Flag.

Returns:

true if set.

getParity

public boolean getParity()

Get state of parity flag.

Returns:

true if set.

getBit3

public boolean getBit3()

Get state of bit 3 flag.

Returns:

true if set.

getHc

public boolean getHc()

Get state of halfcarry flag.

Returns:

true if set.

getBit5

public boolean getBit5()

Get state of bit 5 flag.

Returns:

true if set.

getZero

public boolean getZero()

Get state of zero flag.

Returns:

true if set.

getSign

public boolean getSign()

Get state of sign flag.

Returns:

true if set.

getOp

public java.lang.String getOp()

Return next opcode for debugging purposes.

Returns:

String containing opcode bytes.

getMnu

public java.lang.String getMnu()

Return mnemonic of next opcode for debugging purposes.

Returns:

String containing opcode bytes.

debug

public boolean debug(int cycles)

Run Z80 for a single instruction (debugging purposes).

Parameters:

cycles - machine cycles to run for in total.

Returns:

true if cycles elapsed.

consoledebug

private void consoledebug()

Output contents of Z80 registers to console for debugging purposes.

run

public void run(int cycles)

Run Z80.

Parameters:

cycles - machine cycles to run for in total.

nmi

public void nmi()

Generate Non Maskable Interrupt (NMI).

interrupt

public void interrupt()

Normal interrupt routine.

doOp

private void doOp(int opcode)

Execute opcode.

Parameters:

opcode - opcode hex value

jp

private void jp(boolean condition)

Jump.

Parameters:

condition - if true jump will be taken.

jr

private void jr(boolean condition)

Jump relative.

Parameters:

condition - if true jump will be taken.

call

private void call(boolean condition)

Call.

Parameters:

condition - if true call will be taken.

ret

private void ret(boolean condition)

Return.

Parameters:

condition - if true return will be taken.

push

private void push(int value)

Push value onto stack.

Parameters:

value - value to push

pop

private int pop()

Pop value off stack.

Returns:

value from stack.

inchl

private void inchl(int offset)

INC (HL) - increment memory location.

Parameters:

offset - memory offset to increment.

dechl

private void dechl(int offset)

DEC (HL) - Decrement memory location.

Parameters:

offset - memory offset to increment.

ccf

private void ccf()

CCF - Complement Carry Flag.

daa

private void daa()

DAA - Decimal Adjust Accumulator adds 6 to left and/or right nibble. Pre-Calculated Result For Speed.

doCB

private void doCB(int opcode)

Execute CB prefixed opcode.

Parameters:

opcode - opcode hex value

rlc

private int rlc(int value)

CB RLC - Rotate Left Carry.

Parameters:

value - value to adjust.

Returns:

adjusted value.

rrc

private int rrc(int value)

CB RRC - Rotate Right Carry.

Parameters:

value - value to adjust.

Returns:

adjusted value.

rl

private int rl(int value)

CB RL - Rotate Left.

Parameters:

value - value to adjust.

Returns:

adjusted value.

rr

private int rr(int value)

CB RR - Rotate Right.

Parameters:

value - value to adjust.

Returns:

adjusted value.

sla

private int sla(int value)

CB SLA - Shift Left Arithmetic.

Parameters:

value - value to adjust.

Returns:

adjusted value.

sra

private int sra(int value)

CB SRA - Shift Right Arithmetic.

Parameters:

value - value to adjust.

Returns:

adjusted value.

sll

private int sll(int value)

CB SLL - Logical Left Shift.

Parameters:

value - value to adjust.

Returns:

adjusted value.

srl

private int srl(int value)

CB SRL - Logical Shift Right.

Parameters:

value - value to adjust.

Returns:

adjusted value.

setBit

private int setBit(int value,
                   int b)

CB SET - Set Bit On.

Parameters:

value - value to adjust.

b - bit to turn on.

Returns:

adjusted value.

res

private int res(int value,
                int b)

CB RES - Reset Bit.

Parameters:

value - value to adjust.

b - bit to turn off.

Returns:

adjusted value.

bit

private void bit(int value,
                 int b)

CB BIT - Test Bit.

Parameters:

value - value to test.

b - bit of value to test.

doIndexOp

private void doIndexOp(int opcode,
                       Registers index)

Execute DD/FD Prefixed Index Opcode.

Parameters:

opcode - opcode hex value.

index - index register to use.

d

private int d()

Get Offset Value from memory for index operations.

Returns:

offset.

doIndexCB

private void doIndexCB(Registers index)

Execute DDCB/FDCB Prefixed Opcode.

Parameters:

index - Index Register To Use.

doED

public void doED(int opcode)

Execute ED Prefixed Opcode.

Parameters:

opcode - Opcode hex value.

generateDAATable

private void generateDAATable()

Pre-calculate DAA Table.