2 ; Startup code for cc65 (C128 version)
4 ; This must be the *first* file on the linker command line
8 .export BRKStub, BRKOld, BRKInd
9 .import condes, initlib, donelib
10 .import initconio, doneconio, zerobss
12 .import __IRQFUNC_TABLE__, __IRQFUNC_COUNT__
13 .import __RAM_START__, __RAM_SIZE__
15 .include "zeropage.inc"
17 .include "../cbm/cbm.inc"
19 ; ------------------------------------------------------------------------
22 IRQInd = $2FD ; JMP $0000 - used as indirect IRQ vector
24 ; ------------------------------------------------------------------------
25 ; Place the startup code in a special segment to cope with the quirks of
26 ; c128 banking. Do also create an empty segment named "NMI" to avoid
27 ; warnings if the rs232 routines are not used.
34 ; ------------------------------------------------------------------------
35 ; BASIC header with a SYS call
38 .word Head ; Load address
40 .word 1000 ; Line number
41 .byte $9E,"7181" ; SYS 7181
42 .byte $00 ; End of BASIC line
43 @Next: .word 0 ; BASIC end marker
46 ; ------------------------------------------------------------------------
53 ; Switch to the second charset
58 ; Before doing anything else, we have to setup our banking configuration.
59 ; Otherwise just the lowest 16K are actually RAM. Writing through the ROM
60 ; to the underlying RAM works, but it is bad style.
62 lda MMU_CR ; Get current memory configuration...
63 pha ; ...and save it for later
64 lda #CC65_MMU_CFG ; Bank0 with kernal ROM
67 ; Save the zero page locations we need
79 ; Save system stuff and setup the stack
85 stx spsave ; Save the system stack pointer
87 lda #<(__RAM_START__ + __RAM_SIZE__)
89 lda #>(__RAM_START__ + __RAM_SIZE__)
90 sta sp+1 ; Set argument stack ptr
92 ; Call module constructors
96 ; Initialize conio stuff
100 ; If we have IRQ functions, chain our stub into the IRQ vector
102 lda #<__IRQFUNC_COUNT__
115 ; Pass an empty command line
117 NoIRQ1: jsr push0 ; argc
120 ldy #4 ; Argument size
121 jsr _main ; call the users code
123 ; This is also the _exit entry. Reset the IRQ vector if we chained it.
125 _exit: lda #<__IRQFUNC_COUNT__
134 ; Run module destructors
138 ; Reset the conio stuff
147 ; Copy back the zero page stuff
155 ; Reset the memory configuration
160 ; Done, restore kernal vectors in an attempt to cleanup
164 ; ------------------------------------------------------------------------
165 ; The C128 has ROM parallel to the RAM starting from $4000. The startup code
166 ; above will change this setting so that we have RAM from $0000-$BFFF. This
167 ; works quite well with the exception of interrupts: The interrupt handler
168 ; is in ROM, and the ROM switches back to the ROM configuration, which means
169 ; that parts of our program may not be accessible. Since the crt0 module is
170 ; the first module in the program, it will always be below $4000 and always
171 ; in RAM. So we place several short stubs here that switch back our ROM
172 ; config before calling our user defined handlers. These stubs are only
173 ; used if any other code uses the interrupt or break vectors. They are dead
174 ; code otherwise, but since there is no other way to keep them in low memory,
175 ; they have to go here.
178 cld ; Just to be sure
179 lda MMU_CR ; Get old register value
180 pha ; And save on stack
181 lda #CC65_MMU_CFG ; Bank 0 with kernal ROM
183 ldy #<(__IRQFUNC_COUNT__*2)
184 lda #<__IRQFUNC_TABLE__
185 ldx #>__IRQFUNC_TABLE__
186 jsr condes ; Call the functions
187 pla ; Get old register value
189 jmp IRQInd ; Jump to the save IRQ vector
193 pla ; Get original MMU_CR value
194 sta MMU_CR ; And set it
195 jmp BRKInd ; Jump indirect to break
198 ; ------------------------------------------------------------------------
204 ; Old break vector preceeded by a jump opcode
207 ; Indirect vectors preceeded by a jump opcode