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1This file describes how to use the Z80 processor emulation as a
2standalone module (without the ZX Spectrum emulation).
3
4===========================================================================
5You will need the following files:
6
7For the 'intel x86' assembly version:
8-------------------------------------
9
10z80.c z80.h z80_type.h i386step.S i386def.S i386op1.S i386op1x.S
11i386op2.S i386op2x.S i386op3.S i386op3x.S i386op4.S i386op5.S i386op6.S
12sp_to_s.c
13
14For the 'C' version:
15--------------------
16
17z80.c z80.h z80_type.h z80_step.c z80_def.h z80_ari.h z80optab.c z80optab.h
18z80_op1.c z80_op1x.c z80_op1.h z80_op2.c z80_op2x.c z80_op2.h
19z80_op3.c z80_op3x.c z80_op3.h z80_op4.c z80_op4x.c z80_op4.h
20z80_op5.c z80_op5.h z80_op6.c z80_op6.h
21
22===========================================================================
23Makefile rules:
24
25For the 'intel x86' assembly version:
26-------------------------------------
27
28CC = gcc
29AR = ar
30CPPFLAGS =
31CFLAGS = -Wall -O3
32CPP = $(CC) -E
33
34z80_i386_objs = z80.o i386emul.o
35
36libz80.a: $(z80_i386_objs)
37 $(AR) cr libz80.a $(z80_i386_objs)
38
39i386emul.o: i386emul.s
40 $(CC) -c $(CFLAGS) i386emul.s
41
42i386emul.s: i386emul.sp sp_to_s
43 ./sp_to_s < i386emul.sp > i386emul.s
44
45i386emul.sp: i386step.S
46 $(CPP) $(CPPFLAGS) i386step.S > i386emul.sp
47
48sp_to_s: sp_to_s.o
49 $(CC) -o sp_to_s $(LDFLAGS) sp_to_s.o
50
51.SUFFIXES:
52.SUFFIXES: .c .o
53
54.c.o:
55 $(CC) -c $(CFLAGS) $(CPPFLAGS) $<
56
57
58For 'C' version:
59----------------
60
61CC = gcc
62AR = ar
63CPPFLAGS = -DZ80C
64CFLAGS = -Wall -O3 -fomit-frame-pointer -funroll-loops
65
66z80_c_objs = z80.o z80_step.o z80optab.o z80_op1.o z80_op2.o z80_op3.o \
67 z80_op4.o z80_op5.o z80_op6.o
68
69libz80.a: $(z80_c_objs)
70 $(AR) cr libz80.a $(z80_c_objs)
71
72.SUFFIXES:
73.SUFFIXES: .c .o
74
75.c.o:
76 $(CC) -c $(CFLAGS) $(CPPFLAGS) $<
77
78===========================================================================
79The following functions are defined by libz80.a:
80
81void z80_init()
82---------------
83
84This function initializes the processor emulation. This must be called
85only once at the beginning of the program.
86
87int z80_step(int ticknum)
88-------------------------
89
90This function executes z80 instructions for 'ticknum' number of clock
91cycles. It returns the remaining number of ticks.
92
93NOTE: the remaining number of ticks is always zero or negative,
94meaning that exactly, or more than the given 'ticknum' clock cycles
95were executed. This is because WHOLE instructions are executed at a
96time.
97
98NOTE: HALT, LDDR, etc... do not count as one instruction, but as a
99series of instructions (e.g. HALT is a series of NOPs).
100
101void z80_reset()
102----------------
103
104This function resets the Z80 processor. This has the same effect as
105applying a pulse to the RESET input of the processor.
106
107NOTE: z80_init() does not reset the Z80, z80_reset() should be called
108after it.
109
110void z80_interrupt(int data)
111-----------------------------
112
113Causes a Maskable Interrupt. Interrupt mode 1 and 2 are emulated
114correctly, in interrupt mode 2 'data' is used in the address
115calculation. In interrupt mode 0, it is assumed (as on the ZX
116Spectrum) that 0xFF is on the data bus, and always RST 38 is
117generated.
118
119NOTE: It is not emulated, that in the instruction after EI no
120interrupt can be generated.
121
122void z80_nmi()
123--------------
124
125Causes a Non Maskable Interrupt.
126
127===========================================================================
128Accessing the memory, the I/O ports and the Z80 processor's state
129(i.e. registers, etc...)
130
131To use the functions above and the variables below, include the
132"z80.h" include file.
133
134Memory
135------
136
137The memory is stored in the z80_proc.mem[] byte array, which has a
138size of 65536. By default it is all RAM. To make parts of it read
139only, you have to redefine the appropriate macros in i386step.S and/or
140z80_def.h. (These macros are sorounded by #ifdef SPECT_MEM, #else,
141#endif statements.)
142
143The memory is initialised to random data. You must fill it in before
144starting the emulation, but AFTER the call to z80_init().
145
146I/O
147---
148
149The input port values are stored in z80_inports[] array, which has a
150size of 256. The IN instruction will use the appropriate element of
151this array. This array is initialised to all zeroes.
152
153The output port values can be queried from the z80_outports[] array,
154which has also a size of 256. The OUT instruction will store the value
155in the element addressed by the instruction.
156
157If you need more complex behaviour of the I/O, you must redefine the
158appropriate macros in i386step.S and z80_def.h.
159
160Processor state
161---------------
162
163You can access the processor's state with the following variables and
164macros defined in "z80.h".
165
166Registers:
167
168Double registers:
169 normal: BC, DE, HL, AF, IR, IX, IY, PC, SP,
170 aux: BCBK, DEBK, HLBK, AFBK
171
172Single registers:
173 RB, RC, RD, RE, RH, RL, RA, RF, RI, RR, XH, XL, YH, YL, PCH, PCL, SPH, SPL
174
175Misc state:
176 z80_proc.haltstate (1: processor is in halt mode, 0: processor is runnig)
177 z80_proc.it_mode (interrupt mode 0, 1 or 2)
178 z80_proc.iff1 (interrupt flip-flop 1)
179 z80_proc.iff2 (interrupt flip-flop 2)
180
181You need not access the other parts of z80_proc, they are meaningless
182outside the z80_step() function.