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eh_basic_mk.asm
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eh_basic_mk.asm
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; The code below was copied and adapted from Lee Davison’s
; code of EhBasic to be ran in MKBASIC (VM65) 6502 emulator.
; Original comments and credits follow:
;
; Enhanced BASIC to assemble under 6502 simulator, $ver 2.22
; $E7E1 $E7CF $E7C6 $E7D3 $E7D1 $E7D5 $E7CF $E81E $E825
; 2.00 new revision numbers start here
; 2.01 fixed LCASE$() and UCASE$()
; 2.02 new get value routine done
; 2.03 changed RND() to galoise method
; 2.04 fixed SPC()
; 2.05 new get value routine fixed
; 2.06 changed USR() code
; 2.07 fixed STR$()
; 2.08 changed INPUT and READ to remove need for $00 start to input buffer
; 2.09 fixed RND()
; 2.10 integrated missed changes from an earlier version
; 2.20 added ELSE to IF .. THEN and fixed IF .. GOTO <statement> to cause error
; 2.21 fixed IF .. THEN RETURN to not cause error
; 2.22 fixed RND() breaking the get byte routine
;----------------------------------------------------------------------------
; to assemble run Kowalski's 6502 emulator, assemble code and save as binary
; with no header (65b), from $C000 to $FFFF.
; Then for VM65 emulator, perform conversion to memory image definition:
; bin2hex -f ehbas.65b -o ehbas_xx.dat -w 49152 -x 49152
; Add IO address and enable IO in DAT configuration part.
; This version has RAM top at $B000-1, so the area from $B000 to $BFFF can
; be used for binary code or data (e.g.: character ROM).
;----------------------------------------------------------------------------
; zero page use ..
LAB_WARM = $00 ; BASIC warm start entry point
Wrmjpl = LAB_WARM+1; BASIC warm start vector jump low byte
Wrmjph = LAB_WARM+2; BASIC warm start vector jump high byte
Usrjmp = $0A ; USR function JMP address
Usrjpl = Usrjmp+1 ; USR function JMP vector low byte
Usrjph = Usrjmp+2 ; USR function JMP vector high byte
Nullct = $0D ; nulls output after each line
TPos = $0E ; BASIC terminal position byte
TWidth = $0F ; BASIC terminal width byte
Iclim = $10 ; input column limit
Itempl = $11 ; temporary integer low byte
Itemph = Itempl+1 ; temporary integer high byte
nums_1 = Itempl ; number to bin/hex string convert MSB
nums_2 = nums_1+1 ; number to bin/hex string convert
nums_3 = nums_1+2 ; number to bin/hex string convert LSB
Srchc = $5B ; search character
Temp3 = Srchc ; temp byte used in number routines
Scnquo = $5C ; scan-between-quotes flag
Asrch = Scnquo ; alt search character
XOAw_l = Srchc ; eXclusive OR, OR and AND word low byte
XOAw_h = Scnquo ; eXclusive OR, OR and AND word high byte
Ibptr = $5D ; input buffer pointer
Dimcnt = Ibptr ; # of dimensions
Tindx = Ibptr ; token index
Defdim = $5E ; default DIM flag
Dtypef = $5F ; data type flag, $FF=string, $00=numeric
Oquote = $60 ; open quote flag (b7) (Flag: DATA scan; LIST quote; memory)
Gclctd = $60 ; garbage collected flag
Sufnxf = $61 ; subscript/FNX flag, 1xxx xxx = FN(0xxx xxx)
Imode = $62 ; input mode flag, $00=INPUT, $80=READ
Cflag = $63 ; comparison evaluation flag
TabSiz = $64 ; TAB step size (was input flag)
next_s = $65 ; next descriptor stack address
; these two bytes form a word pointer to the item
; currently on top of the descriptor stack
last_sl = $66 ; last descriptor stack address low byte
last_sh = $67 ; last descriptor stack address high byte (always $00)
des_sk = $68 ; descriptor stack start address (temp strings)
; = $70 ; End of descriptor stack
ut1_pl = $71 ; utility pointer 1 low byte
ut1_ph = ut1_pl+1 ; utility pointer 1 high byte
ut2_pl = $73 ; utility pointer 2 low byte
ut2_ph = ut2_pl+1 ; utility pointer 2 high byte
Temp_2 = ut1_pl ; temp byte for block move
FACt_1 = $75 ; FAC temp mantissa1
FACt_2 = FACt_1+1 ; FAC temp mantissa2
FACt_3 = FACt_2+1 ; FAC temp mantissa3
dims_l = FACt_2 ; array dimension size low byte
dims_h = FACt_3 ; array dimension size high byte
TempB = $78 ; temp page 0 byte
Smeml = $79 ; start of mem low byte (Start-of-Basic)
Smemh = Smeml+1 ; start of mem high byte (Start-of-Basic)
Svarl = $7B ; start of vars low byte (Start-of-Variables)
Svarh = Svarl+1 ; start of vars high byte (Start-of-Variables)
Sarryl = $7D ; var mem end low byte (Start-of-Arrays)
Sarryh = Sarryl+1 ; var mem end high byte (Start-of-Arrays)
Earryl = $7F ; array mem end low byte (End-of-Arrays)
Earryh = Earryl+1 ; array mem end high byte (End-of-Arrays)
Sstorl = $81 ; string storage low byte (String storage (moving down))
Sstorh = Sstorl+1 ; string storage high byte (String storage (moving down))
Sutill = $83 ; string utility ptr low byte
Sutilh = Sutill+1 ; string utility ptr high byte
Ememl = $85 ; end of mem low byte (Limit-of-memory)
Ememh = Ememl+1 ; end of mem high byte (Limit-of-memory)
Clinel = $87 ; current line low byte (Basic line number)
Clineh = Clinel+1 ; current line high byte (Basic line number)
Blinel = $89 ; break line low byte (Previous Basic line number)
Blineh = Blinel+1 ; break line high byte (Previous Basic line number)
Cpntrl = $8B ; continue pointer low byte
Cpntrh = Cpntrl+1 ; continue pointer high byte
Dlinel = $8D ; current DATA line low byte
Dlineh = Dlinel+1 ; current DATA line high byte
Dptrl = $8F ; DATA pointer low byte
Dptrh = Dptrl+1 ; DATA pointer high byte
Rdptrl = $91 ; read pointer low byte
Rdptrh = Rdptrl+1 ; read pointer high byte
Varnm1 = $93 ; current var name 1st byte
Varnm2 = Varnm1+1 ; current var name 2nd byte
Cvaral = $95 ; current var address low byte
Cvarah = Cvaral+1 ; current var address high byte
Frnxtl = $97 ; var pointer for FOR/NEXT low byte
Frnxth = Frnxtl+1 ; var pointer for FOR/NEXT high byte
Tidx1 = Frnxtl ; temp line index
Lvarpl = Frnxtl ; let var pointer low byte
Lvarph = Frnxth ; let var pointer high byte
prstk = $99 ; precedence stacked flag
comp_f = $9B ; compare function flag, bits 0,1 and 2 used
; bit 2 set if >
; bit 1 set if =
; bit 0 set if <
func_l = $9C ; function pointer low byte
func_h = func_l+1 ; function pointer high byte
garb_l = func_l ; garbage collection working pointer low byte
garb_h = func_h ; garbage collection working pointer high byte
des_2l = $9E ; string descriptor_2 pointer low byte
des_2h = des_2l+1 ; string descriptor_2 pointer high byte
g_step = $A0 ; garbage collect step size
Fnxjmp = $A1 ; jump vector for functions
Fnxjpl = Fnxjmp+1 ; functions jump vector low byte
Fnxjph = Fnxjmp+2 ; functions jump vector high byte
g_indx = Fnxjpl ; garbage collect temp index
FAC2_r = $A3 ; FAC2 rounding byte
Adatal = $A4 ; array data pointer low byte
Adatah = Adatal+1 ; array data pointer high byte
Nbendl = Adatal ; new block end pointer low byte
Nbendh = Adatah ; new block end pointer high byte
Obendl = $A6 ; old block end pointer low byte
Obendh = Obendl+1 ; old block end pointer high byte
numexp = $A8 ; string to float number exponent count
expcnt = $A9 ; string to float exponent count
numbit = numexp ; bit count for array element calculations
numdpf = $AA ; string to float decimal point flag
expneg = $AB ; string to float eval exponent -ve flag
Astrtl = numdpf ; array start pointer low byte
Astrth = expneg ; array start pointer high byte
Histrl = numdpf ; highest string low byte
Histrh = expneg ; highest string high byte
Baslnl = numdpf ; BASIC search line pointer low byte
Baslnh = expneg ; BASIC search line pointer high byte
Fvar_l = numdpf ; find/found variable pointer low byte
Fvar_h = expneg ; find/found variable pointer high byte
Ostrtl = numdpf ; old block start pointer low byte
Ostrth = expneg ; old block start pointer high byte
Vrschl = numdpf ; variable search pointer low byte
Vrschh = expneg ; variable search pointer high byte
FAC1_e = $AC ; FAC1 exponent
FAC1_1 = FAC1_e+1 ; FAC1 mantissa1
FAC1_2 = FAC1_e+2 ; FAC1 mantissa2
FAC1_3 = FAC1_e+3 ; FAC1 mantissa3
FAC1_s = FAC1_e+4 ; FAC1 sign (b7)
str_ln = FAC1_e ; string length
str_pl = FAC1_1 ; string pointer low byte
str_ph = FAC1_2 ; string pointer high byte
des_pl = FAC1_2 ; string descriptor pointer low byte
des_ph = FAC1_3 ; string descriptor pointer high byte
mids_l = FAC1_3 ; MID$ string temp length byte
negnum = $B1 ; string to float eval -ve flag
numcon = $B1 ; series evaluation constant count
FAC1_o = $B2 ; FAC1 overflow byte
FAC2_e = $B3 ; FAC2 exponent
FAC2_1 = FAC2_e+1 ; FAC2 mantissa1
FAC2_2 = FAC2_e+2 ; FAC2 mantissa2
FAC2_3 = FAC2_e+3 ; FAC2 mantissa3
FAC2_s = FAC2_e+4 ; FAC2 sign (b7)
FAC_sc = $B8 ; FAC sign comparison, Acc#1 vs #2
FAC1_r = $B9 ; FAC1 rounding byte
ssptr_l = FAC_sc ; string start pointer low byte
ssptr_h = FAC1_r ; string start pointer high byte
sdescr = FAC_sc ; string descriptor pointer
csidx = $BA ; line crunch save index
Asptl = csidx ; array size/pointer low byte
Aspth = $BB ; array size/pointer high byte
Btmpl = Asptl ; BASIC pointer temp low byte
Btmph = Aspth ; BASIC pointer temp low byte
Cptrl = Asptl ; BASIC pointer temp low byte
Cptrh = Aspth ; BASIC pointer temp low byte
Sendl = Asptl ; BASIC pointer temp low byte
Sendh = Aspth ; BASIC pointer temp low byte
LAB_IGBY = $BC ; get next BASIC byte subroutine
LAB_GBYT = $C2 ; get current BASIC byte subroutine
Bpntrl = $C3 ; BASIC execute (get byte) pointer low byte
Bpntrh = Bpntrl+1 ; BASIC execute (get byte) pointer high byte
; = $D7 ; end of get BASIC char subroutine
Rbyte4 = $D8 ; extra PRNG byte
Rbyte1 = Rbyte4+1 ; most significant PRNG byte
Rbyte2 = Rbyte4+2 ; middle PRNG byte
Rbyte3 = Rbyte4+3 ; least significant PRNG byte
NmiBase = $DC ; NMI handler enabled/setup/triggered flags
; bit function
; === ========
; 7 interrupt enabled
; 6 interrupt setup
; 5 interrupt happened
; = $DD ; NMI handler addr low byte
; = $DE ; NMI handler addr high byte
IrqBase = $DF ; IRQ handler enabled/setup/triggered flags
; = $E0 ; IRQ handler addr low byte
; = $E1 ; IRQ handler addr high byte
; = $DE ; unused
; = $DF ; unused
; = $E0 ; unused
; = $E1 ; unused
; = $E2 ; unused
; = $E3 ; unused
; = $E4 ; unused
; = $E5 ; unused
; = $E6 ; unused
; = $E7 ; unused
; = $E8 ; unused
; = $E9 ; unused
; = $EA ; unused
; = $EB ; unused
; = $EC ; unused
; = $ED ; unused
; = $EE ; unused
Decss = $EF ; number to decimal string start
Decssp1 = Decss+1 ; number to decimal string start
; = $FF ; decimal string end
; token values needed for BASIC
; primary command tokens (can start a statement)
TK_END = $80 ; END token
TK_FOR = TK_END+1 ; FOR token
TK_NEXT = TK_FOR+1 ; NEXT token
TK_DATA = TK_NEXT+1 ; DATA token
TK_INPUT = TK_DATA+1 ; INPUT token
TK_DIM = TK_INPUT+1 ; DIM token
TK_READ = TK_DIM+1 ; READ token
TK_LET = TK_READ+1 ; LET token
TK_DEC = TK_LET+1 ; DEC token
TK_GOTO = TK_DEC+1 ; GOTO token
TK_RUN = TK_GOTO+1 ; RUN token
TK_IF = TK_RUN+1 ; IF token
TK_RESTORE = TK_IF+1 ; RESTORE token
TK_GOSUB = TK_RESTORE+1 ; GOSUB token
TK_RETIRQ = TK_GOSUB+1 ; RETIRQ token
TK_RETNMI = TK_RETIRQ+1 ; RETNMI token
TK_RETURN = TK_RETNMI+1 ; RETURN token
TK_REM = TK_RETURN+1 ; REM token
TK_STOP = TK_REM+1 ; STOP token
TK_ON = TK_STOP+1 ; ON token
TK_NULL = TK_ON+1 ; NULL token
TK_INC = TK_NULL+1 ; INC token
TK_WAIT = TK_INC+1 ; WAIT token
TK_LOAD = TK_WAIT+1 ; LOAD token
TK_SAVE = TK_LOAD+1 ; SAVE token
TK_DEF = TK_SAVE+1 ; DEF token
TK_POKE = TK_DEF+1 ; POKE token
TK_DOKE = TK_POKE+1 ; DOKE token
TK_CALL = TK_DOKE+1 ; CALL token
TK_DO = TK_CALL+1 ; DO token
TK_LOOP = TK_DO+1 ; LOOP token
TK_PRINT = TK_LOOP+1 ; PRINT token
TK_CONT = TK_PRINT+1 ; CONT token
TK_LIST = TK_CONT+1 ; LIST token
TK_CLEAR = TK_LIST+1 ; CLEAR token
TK_NEW = TK_CLEAR+1 ; NEW token
TK_WIDTH = TK_NEW+1 ; WIDTH token
TK_GET = TK_WIDTH+1 ; GET token
TK_SWAP = TK_GET+1 ; SWAP token
TK_BITSET = TK_SWAP+1 ; BITSET token
TK_BITCLR = TK_BITSET+1 ; BITCLR token
TK_IRQ = TK_BITCLR+1 ; IRQ token
TK_NMI = TK_IRQ+1 ; NMI token
; secondary command tokens, can't start a statement
TK_TAB = TK_NMI+1 ; TAB token
TK_ELSE = TK_TAB+1 ; ELSE token
TK_TO = TK_ELSE+1 ; TO token
TK_FN = TK_TO+1 ; FN token
TK_SPC = TK_FN+1 ; SPC token
TK_THEN = TK_SPC+1 ; THEN token
TK_NOT = TK_THEN+1 ; NOT token
TK_STEP = TK_NOT+1 ; STEP token
TK_UNTIL = TK_STEP+1 ; UNTIL token
TK_WHILE = TK_UNTIL+1 ; WHILE token
TK_OFF = TK_WHILE+1 ; OFF token
; opperator tokens
TK_PLUS = TK_OFF+1 ; + token
TK_MINUS = TK_PLUS+1 ; - token
TK_MUL = TK_MINUS+1 ; * token
TK_DIV = TK_MUL+1 ; / token
TK_POWER = TK_DIV+1 ; ^ token
TK_AND = TK_POWER+1 ; AND token
TK_EOR = TK_AND+1 ; EOR token
TK_OR = TK_EOR+1 ; OR token
TK_RSHIFT = TK_OR+1 ; RSHIFT token
TK_LSHIFT = TK_RSHIFT+1 ; LSHIFT token
TK_GT = TK_LSHIFT+1 ; > token
TK_EQUAL = TK_GT+1 ; = token
TK_LT = TK_EQUAL+1 ; < token
; functions tokens
TK_SGN = TK_LT+1 ; SGN token
TK_INT = TK_SGN+1 ; INT token
TK_ABS = TK_INT+1 ; ABS token
TK_USR = TK_ABS+1 ; USR token
TK_FRE = TK_USR+1 ; FRE token
TK_POS = TK_FRE+1 ; POS token
TK_SQR = TK_POS+1 ; SQR token
TK_RND = TK_SQR+1 ; RND token
TK_LOG = TK_RND+1 ; LOG token
TK_EXP = TK_LOG+1 ; EXP token
TK_COS = TK_EXP+1 ; COS token
TK_SIN = TK_COS+1 ; SIN token
TK_TAN = TK_SIN+1 ; TAN token
TK_ATN = TK_TAN+1 ; ATN token
TK_PEEK = TK_ATN+1 ; PEEK token
TK_DEEK = TK_PEEK+1 ; DEEK token
TK_SADD = TK_DEEK+1 ; SADD token
TK_LEN = TK_SADD+1 ; LEN token
TK_STRS = TK_LEN+1 ; STR$ token
TK_VAL = TK_STRS+1 ; VAL token
TK_ASC = TK_VAL+1 ; ASC token
TK_UCASES = TK_ASC+1 ; UCASE$ token
TK_LCASES = TK_UCASES+1 ; LCASE$ token
TK_CHRS = TK_LCASES+1 ; CHR$ token
TK_HEXS = TK_CHRS+1 ; HEX$ token
TK_BINS = TK_HEXS+1 ; BIN$ token
TK_BITTST = TK_BINS+1 ; BITTST token
TK_MAX = TK_BITTST+1 ; MAX token
TK_MIN = TK_MAX+1 ; MIN token
TK_PI = TK_MIN+1 ; PI token
TK_TWOPI = TK_PI+1 ; TWOPI token
TK_VPTR = TK_TWOPI+1 ; VARPTR token
TK_LEFTS = TK_VPTR+1 ; LEFT$ token
TK_RIGHTS = TK_LEFTS+1 ; RIGHT$ token
TK_MIDS = TK_RIGHTS+1 ; MID$ token
; offsets from a base of X or Y
PLUS_0 = $00 ; X or Y plus 0
PLUS_1 = $01 ; X or Y plus 1
PLUS_2 = $02 ; X or Y plus 2
PLUS_3 = $03 ; X or Y plus 3
LAB_STAK = $0100 ; stack bottom, no offset
LAB_SKFE = LAB_STAK+$FE
; flushed stack address
LAB_SKFF = LAB_STAK+$FF
; flushed stack address
ccflag = $0200 ; BASIC CTRL-C flag, 00 = enabled, 01 = dis
ccbyte = ccflag+1 ; BASIC CTRL-C byte
ccnull = ccbyte+1 ; BASIC CTRL-C byte timeout
VEC_CC = ccnull+1 ; ctrl c check vector
VEC_IN = VEC_CC+2 ; input vector
VEC_OUT = VEC_IN+2 ; output vector
VEC_LD = VEC_OUT+2 ; load vector
VEC_SV = VEC_LD+2 ; save vector
; Ibuffs can now be anywhere in RAM, ensure that the max length is < $80
IRQ_vec = VEC_SV+2
Ibuffs = IRQ_vec+$14 ; start of input buffer after IRQ/NMI code
Ibuffe = Ibuffs+$47 ; end of input buffer
.ORG $FFC0
; I/O routines for MKBASIC (V65) emulator.
CHRIN
LDA $FFE1 ; Read from char IO address, non-blocking
BEQ ECHRIN ; if null, assume no character in buffer
CMP #'a' ; < 'a'?
BCC DCHRIN ; yes, done
CMP #'{' ; >= '{'?
BCS DCHRIN ; yes, done
AND #$5F ; no, convert to upper case
DCHRIN
SEC ; These is character waiting, set CARRY flag
RTS
ECHRIN
CLC ; no character in buffer, clear CARRY
RTS
CHROUT
STA $FFE0 ; write to char IO address
AND #$FF ; set flags
RTS
Ram_base = $0300 ; start of user RAM (set as needed, should be page aligned)
Ram_top = $B000 ; end of user RAM+1 (set as needed, should be page aligned)
; This start can be changed to suit your system
*= $C000
; BASIC cold start entry point
; new page 2 initialisation, copy block to ccflag on
LAB_COLD
CLD
LDY #PG2_TABE-PG2_TABS-1
; byte count-1
LAB_2D13
LDA PG2_TABS,Y ; get byte
STA ccflag,Y ; store in page 2
DEY ; decrement count
BPL LAB_2D13 ; loop if not done
LDX #$FF ; set byte
STX Ibuffs
STX Clineh ; set current line high byte (set immediate mode)
TXS ; reset stack pointer
LDA #$4C ; code for JMP
STA Fnxjmp ; save for jump vector for functions
; copy block from LAB_2CEE to $00BC - $00D3
LDX #StrTab-LAB_2CEE ; set byte count
LAB_2D4E
LDA LAB_2CEE-1,X ; get byte from table
STA LAB_IGBY-1,X ; save byte in page zero
DEX ; decrement count
BNE LAB_2D4E ; loop if not all done
; copy block from StrTab to $0000 - $0012
LAB_GMEM
LDX #EndTab-StrTab-1 ; set byte count-1
TabLoop
LDA StrTab,X ; get byte from table
STA PLUS_0,X ; save byte in page zero
DEX ; decrement count
BPL TabLoop ; loop if not all done
; set-up start values
LDA #$00 ; clear A
STA NmiBase ; clear NMI handler enabled flag
STA IrqBase ; clear IRQ handler enabled flag
STA FAC1_o ; clear FAC1 overflow byte
STA last_sh ; clear descriptor stack top item pointer high byte
LDA #$0E ; set default tab size
STA TabSiz ; save it
LDA #$03 ; set garbage collect step size for descriptor stack
STA g_step ; save it
LDX #des_sk ; descriptor stack start
STX next_s ; set descriptor stack pointer
JSR LAB_CRLF ; print CR/LF
LDA #<LAB_MSZM ; point to memory size message (low addr)
LDY #>LAB_MSZM ; point to memory size message (high addr)
JSR LAB_18C3 ; print null terminated string from memory
JSR LAB_INLN ; print "? " and get BASIC input
STX Bpntrl ; set BASIC execute pointer low byte
STY Bpntrh ; set BASIC execute pointer high byte
JSR LAB_GBYT ; get last byte back
BNE LAB_2DAA ; branch if not null (user typed something)
LDY #$00 ; else clear Y
; character was null so get memory size the hard way
; we get here with Y=0 and Itempl/h = Ram_base
LAB_2D93
INC Itempl ; increment temporary integer low byte
BNE LAB_2D99 ; branch if no overflow
INC Itemph ; increment temporary integer high byte
LDA Itemph ; get high byte
CMP #>Ram_top ; compare with top of RAM+1
BEQ LAB_2DB6 ; branch if match (end of user RAM)
LAB_2D99
LDA #$55 ; set test byte
STA (Itempl),Y ; save via temporary integer
CMP (Itempl),Y ; compare via temporary integer
BNE LAB_2DB6 ; branch if fail
ASL ; shift test byte left (now $AA)
STA (Itempl),Y ; save via temporary integer
CMP (Itempl),Y ; compare via temporary integer
BEQ LAB_2D93 ; if ok go do next byte
BNE LAB_2DB6 ; branch if fail
LAB_2DAA
JSR LAB_2887 ; get FAC1 from string
LDA FAC1_e ; get FAC1 exponent
CMP #$98 ; compare with exponent = 2^24
BCS LAB_GMEM ; if too large go try again
JSR LAB_F2FU ; save integer part of FAC1 in temporary integer
; (no range check)
LAB_2DB6
LDA Itempl ; get temporary integer low byte
LDY Itemph ; get temporary integer high byte
CPY #<Ram_base+1 ; compare with start of RAM+$100 high byte
BCC LAB_GMEM ; if too small go try again
; uncomment these lines if you want to check on the high limit of memory. Note if
; Ram_top is set too low then this will fail. default is ignore it and assume the
; users know what they're doing!
; CPY #>Ram_top ; compare with top of RAM high byte
; BCC MEM_OK ; branch if < RAM top
; BNE LAB_GMEM ; if too large go try again
; else was = so compare low bytes
; CMP #<Ram_top ; compare with top of RAM low byte
; BEQ MEM_OK ; branch if = RAM top
; BCS LAB_GMEM ; if too large go try again
;MEM_OK
STA Ememl ; set end of mem low byte
STY Ememh ; set end of mem high byte
STA Sstorl ; set bottom of string space low byte
STY Sstorh ; set bottom of string space high byte
LDY #<Ram_base ; set start addr low byte
LDX #>Ram_base ; set start addr high byte
STY Smeml ; save start of mem low byte
STX Smemh ; save start of mem high byte
; this line is only needed if Ram_base is not $xx00
; LDY #$00 ; clear Y
TYA ; clear A
STA (Smeml),Y ; clear first byte
INC Smeml ; increment start of mem low byte
; these two lines are only needed if Ram_base is $xxFF
; BNE LAB_2E05 ; branch if no rollover
; INC Smemh ; increment start of mem high byte
LAB_2E05
JSR LAB_CRLF ; print CR/LF
JSR LAB_1463 ; do "NEW" and "CLEAR"
LDA Ememl ; get end of mem low byte
SEC ; set carry for subtract
SBC Smeml ; subtract start of mem low byte
TAX ; copy to X
LDA Ememh ; get end of mem high byte
SBC Smemh ; subtract start of mem high byte
JSR LAB_295E ; print XA as unsigned integer (bytes free)
LDA #<LAB_SMSG ; point to sign-on message (low addr)
LDY #>LAB_SMSG ; point to sign-on message (high addr)
JSR LAB_18C3 ; print null terminated string from memory
LDA #<LAB_1274 ; warm start vector low byte
LDY #>LAB_1274 ; warm start vector high byte
STA Wrmjpl ; save warm start vector low byte
STY Wrmjph ; save warm start vector high byte
JMP (Wrmjpl) ; go do warm start
; open up space in memory
; move (Ostrtl)-(Obendl) to new block ending at (Nbendl)
; Nbendl,Nbendh - new block end address (A/Y)
; Obendl,Obendh - old block end address
; Ostrtl,Ostrth - old block start address
; returns with ..
; Nbendl,Nbendh - new block start address (high byte - $100)
; Obendl,Obendh - old block start address (high byte - $100)
; Ostrtl,Ostrth - old block start address (unchanged)
LAB_11CF
JSR LAB_121F ; check available memory, "Out of memory" error if no room
; addr to check is in AY (low/high)
STA Earryl ; save new array mem end low byte
STY Earryh ; save new array mem end high byte
; open up space in memory
; move (Ostrtl)-(Obendl) to new block ending at (Nbendl)
; don't set array end
LAB_11D6
SEC ; set carry for subtract
LDA Obendl ; get block end low byte
SBC Ostrtl ; subtract block start low byte
TAY ; copy MOD(block length/$100) byte to Y
LDA Obendh ; get block end high byte
SBC Ostrth ; subtract block start high byte
TAX ; copy block length high byte to X
INX ; +1 to allow for count=0 exit
TYA ; copy block length low byte to A
BEQ LAB_120A ; branch if length low byte=0
; block is (X-1)*256+Y bytes, do the Y bytes first
SEC ; set carry for add + 1, two's complement
EOR #$FF ; invert low byte for subtract
ADC Obendl ; add block end low byte
STA Obendl ; save corrected old block end low byte
BCS LAB_11F3 ; branch if no underflow
DEC Obendh ; else decrement block end high byte
SEC ; set carry for add + 1, two's complement
LAB_11F3
TYA ; get MOD(block length/$100) byte
EOR #$FF ; invert low byte for subtract
ADC Nbendl ; add destination end low byte
STA Nbendl ; save modified new block end low byte
BCS LAB_1203 ; branch if no underflow
DEC Nbendh ; else decrement block end high byte
BCC LAB_1203 ; branch always
LAB_11FF
LDA (Obendl),Y ; get byte from source
STA (Nbendl),Y ; copy byte to destination
LAB_1203
DEY ; decrement index
BNE LAB_11FF ; loop until Y=0
; now do Y=0 indexed byte
LDA (Obendl),Y ; get byte from source
STA (Nbendl),Y ; save byte to destination
LAB_120A
DEC Obendh ; decrement source pointer high byte
DEC Nbendh ; decrement destination pointer high byte
DEX ; decrement block count
BNE LAB_1203 ; loop until count = $0
RTS
; check room on stack for A bytes
; stack too deep? do OM error
LAB_1212
STA TempB ; save result in temp byte
TSX ; copy stack
CPX TempB ; compare new "limit" with stack
BCC LAB_OMER ; if stack < limit do "Out of memory" error then warm start
RTS
; check available memory, "Out of memory" error if no room
; addr to check is in AY (low/high)
LAB_121F
CPY Sstorh ; compare bottom of string mem high byte
BCC LAB_124B ; if less then exit (is ok)
BNE LAB_1229 ; skip next test if greater (tested <)
; high byte was =, now do low byte
CMP Sstorl ; compare with bottom of string mem low byte
BCC LAB_124B ; if less then exit (is ok)
; addr is > string storage ptr (oops!)
LAB_1229
PHA ; push addr low byte
LDX #$08 ; set index to save Adatal to expneg inclusive
TYA ; copy addr high byte (to push on stack)
; save misc numeric work area
LAB_122D
PHA ; push byte
LDA Adatal-1,X ; get byte from Adatal to expneg ( ,$00 not pushed)
DEX ; decrement index
BPL LAB_122D ; loop until all done
JSR LAB_GARB ; garbage collection routine
; restore misc numeric work area
LDX #$00 ; clear the index to restore bytes
LAB_1238
PLA ; pop byte
STA Adatal,X ; save byte to Adatal to expneg
INX ; increment index
CPX #$08 ; compare with end + 1
BMI LAB_1238 ; loop if more to do
PLA ; pop addr high byte
TAY ; copy back to Y
PLA ; pop addr low byte
CPY Sstorh ; compare bottom of string mem high byte
BCC LAB_124B ; if less then exit (is ok)
BNE LAB_OMER ; if greater do "Out of memory" error then warm start
; high byte was =, now do low byte
CMP Sstorl ; compare with bottom of string mem low byte
BCS LAB_OMER ; if >= do "Out of memory" error then warm start
; ok exit, carry clear
LAB_124B
RTS
; do "Out of memory" error then warm start
LAB_OMER
LDX #$0C ; error code $0C ("Out of memory" error)
; do error #X, then warm start
LAB_XERR
JSR LAB_CRLF ; print CR/LF
LDA LAB_BAER,X ; get error message pointer low byte
LDY LAB_BAER+1,X ; get error message pointer high byte
JSR LAB_18C3 ; print null terminated string from memory
JSR LAB_1491 ; flush stack and clear continue flag
LDA #<LAB_EMSG ; point to " Error" low addr
LDY #>LAB_EMSG ; point to " Error" high addr
LAB_1269
JSR LAB_18C3 ; print null terminated string from memory
LDY Clineh ; get current line high byte
INY ; increment it
BEQ LAB_1274 ; go do warm start (was immediate mode)
; else print line number
JSR LAB_2953 ; print " in line [LINE #]"
; BASIC warm start entry point
; wait for Basic command
LAB_1274
; clear ON IRQ/NMI bytes
LDA #$00 ; clear A
STA IrqBase ; clear enabled byte
STA NmiBase ; clear enabled byte
LDA #<LAB_RMSG ; point to "Ready" message low byte
LDY #>LAB_RMSG ; point to "Ready" message high byte
JSR LAB_18C3 ; go do print string
CLC
; wait for Basic command (no "Ready")
LAB_127D
JSR LAB_1357 ; call for BASIC input
LAB_1280
STX Bpntrl ; set BASIC execute pointer low byte
STY Bpntrh ; set BASIC execute pointer high byte
JSR LAB_GBYT ; scan memory
BEQ LAB_127D ; loop while null
; got to interpret input line now ..
LDX #$FF ; current line to null value
STX Clineh ; set current line high byte
BCC LAB_1295 ; branch if numeric character (handle new BASIC line)
; no line number .. immediate mode
JSR LAB_13A6 ; crunch keywords into Basic tokens
JMP LAB_15F6 ; go scan and interpret code
; handle new BASIC line
LAB_1295
JSR LAB_GFPN ; get fixed-point number into temp integer
JSR LAB_13A6 ; crunch keywords into Basic tokens
STY Ibptr ; save index pointer to end of crunched line
JSR LAB_SSLN ; search BASIC for temp integer line number
BCC LAB_12E6 ; branch if not found
; aroooogah! line # already exists! delete it
LDY #$01 ; set index to next line pointer high byte
LDA (Baslnl),Y ; get next line pointer high byte
STA ut1_ph ; save it
LDA Svarl ; get start of vars low byte
STA ut1_pl ; save it
LDA Baslnh ; get found line pointer high byte
STA ut2_ph ; save it
LDA Baslnl ; get found line pointer low byte
DEY ; decrement index
SBC (Baslnl),Y ; subtract next line pointer low byte
CLC ; clear carry for add
ADC Svarl ; add start of vars low byte
STA Svarl ; save new start of vars low byte
STA ut2_pl ; save destination pointer low byte
LDA Svarh ; get start of vars high byte
ADC #$FF ; -1 + carry
STA Svarh ; save start of vars high byte
SBC Baslnh ; subtract found line pointer high byte
TAX ; copy to block count
SEC ; set carry for subtract
LDA Baslnl ; get found line pointer low byte
SBC Svarl ; subtract start of vars low byte
TAY ; copy to bytes in first block count
BCS LAB_12D0 ; branch if overflow
INX ; increment block count (correct for =0 loop exit)
DEC ut2_ph ; decrement destination high byte
LAB_12D0
CLC ; clear carry for add
ADC ut1_pl ; add source pointer low byte
BCC LAB_12D8 ; branch if no overflow
DEC ut1_ph ; else decrement source pointer high byte
CLC ; clear carry
; close up memory to delete old line
LAB_12D8
LDA (ut1_pl),Y ; get byte from source
STA (ut2_pl),Y ; copy to destination
INY ; increment index
BNE LAB_12D8 ; while <> 0 do this block
INC ut1_ph ; increment source pointer high byte
INC ut2_ph ; increment destination pointer high byte
DEX ; decrement block count
BNE LAB_12D8 ; loop until all done
; got new line in buffer and no existing same #
LAB_12E6
LDA Ibuffs ; get byte from start of input buffer
BEQ LAB_1319 ; if null line just go flush stack/vars and exit
; got new line and it isn't empty line
LDA Ememl ; get end of mem low byte
LDY Ememh ; get end of mem high byte
STA Sstorl ; set bottom of string space low byte
STY Sstorh ; set bottom of string space high byte
LDA Svarl ; get start of vars low byte (end of BASIC)
STA Obendl ; save old block end low byte
LDY Svarh ; get start of vars high byte (end of BASIC)
STY Obendh ; save old block end high byte
ADC Ibptr ; add input buffer pointer (also buffer length)
BCC LAB_1301 ; branch if no overflow from add
INY ; else increment high byte
LAB_1301
STA Nbendl ; save new block end low byte (move to, low byte)
STY Nbendh ; save new block end high byte
JSR LAB_11CF ; open up space in memory
; old start pointer Ostrtl,Ostrth set by the find line call
LDA Earryl ; get array mem end low byte
LDY Earryh ; get array mem end high byte
STA Svarl ; save start of vars low byte
STY Svarh ; save start of vars high byte
LDY Ibptr ; get input buffer pointer (also buffer length)
DEY ; adjust for loop type
LAB_1311
LDA Ibuffs-4,Y ; get byte from crunched line
STA (Baslnl),Y ; save it to program memory
DEY ; decrement count
CPY #$03 ; compare with first byte-1
BNE LAB_1311 ; continue while count <> 3
LDA Itemph ; get line # high byte
STA (Baslnl),Y ; save it to program memory
DEY ; decrement count
LDA Itempl ; get line # low byte
STA (Baslnl),Y ; save it to program memory
DEY ; decrement count
LDA #$FF ; set byte to allow chain rebuild. if you didn't set this
; byte then a zero already here would stop the chain rebuild
; as it would think it was the [EOT] marker.
STA (Baslnl),Y ; save it to program memory
LAB_1319
JSR LAB_1477 ; reset execution to start, clear vars and flush stack
LDX Smeml ; get start of mem low byte
LDA Smemh ; get start of mem high byte
LDY #$01 ; index to high byte of next line pointer
LAB_1325
STX ut1_pl ; set line start pointer low byte
STA ut1_ph ; set line start pointer high byte
LDA (ut1_pl),Y ; get it
BEQ LAB_133E ; exit if end of program
; rebuild chaining of Basic lines
LDY #$04 ; point to first code byte of line
; there is always 1 byte + [EOL] as null entries are deleted
LAB_1330
INY ; next code byte
LDA (ut1_pl),Y ; get byte
BNE LAB_1330 ; loop if not [EOL]
SEC ; set carry for add + 1
TYA ; copy end index
ADC ut1_pl ; add to line start pointer low byte
TAX ; copy to X
LDY #$00 ; clear index, point to this line's next line pointer
STA (ut1_pl),Y ; set next line pointer low byte
TYA ; clear A
ADC ut1_ph ; add line start pointer high byte + carry
INY ; increment index to high byte
STA (ut1_pl),Y ; save next line pointer low byte
BCC LAB_1325 ; go do next line, branch always, carry clear
LAB_133E
JMP LAB_127D ; else we just wait for Basic command, no "Ready"
; print "? " and get BASIC input
LAB_INLN
JSR LAB_18E3 ; print "?" character
JSR LAB_18E0 ; print " "
BNE LAB_1357 ; call for BASIC input and return
; receive line from keyboard
; $08 as delete key (BACKSPACE on standard keyboard)
LAB_134B
JSR LAB_PRNA ; go print the character
DEX ; decrement the buffer counter (delete)
.byte $2C ; make LDX into BIT abs