CPU-Z80-Disassembler
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t/data/zx48_base.asm view on Meta::CPAN
scf ; Set Carry Flag
ret nz ; return with carry set if at end
; of program. ->
ld b,(hl) ; high byte of line number to B
inc hl
ld c,(hl) ; low byte to C.
ld (0x5C42),bc ; set system variable NEWPPC.
inc hl
ld c,(hl) ; low byte of line length to C.
inc hl
ld b,(hl) ; high byte to B.
push hl ; save address
add hl,bc ; add length to position.
ld b,h ; and save result
ld c,l ; in BC.
pop hl ; restore address.
ld d,0x00 ; initialize statement counter to zero.
;; LOOK-P-2
LOOK_P_2:
push bc ; save address of next line
call EACH_STMT ; routine EACH-STMT searches current line.
pop bc ; restore address.
ret nc ; return if match was found. ->
jr LOOK_P_1 ; back to LOOK-P-1 for next line.
; -------------------
; Handle NEXT command
; -------------------
; e.g. NEXT i
; The parameter tables have already evaluated the presence of a variable
;; NEXT
NEXT:
bit 1,(iy+0x37) ; test FLAGX - handling a new variable ?
jp nz,REPORT_2 ; jump back to REPORT-2 if so
; 'Variable not found'
; now test if found variable is a simple variable uninitialized by a FOR.
ld hl,(0x5C4D) ; load address of variable from DEST
bit 7,(hl) ; is it correct type ?
jr z,REPORT_1 ; forward to REPORT-1 if not
; 'NEXT without FOR'
inc hl ; step past variable name
ld (0x5C68),hl ; and set MEM to point to three 5-byte values
; value, limit, step.
rst 0x28 ; ; FP-CALC add step and re-store
defb 0xE0 ; ;get-mem-0 v.
defb 0xE2 ; ;get-mem-2 v,s.
defb 0x0F ; ;addition v+s.
defb 0xC0 ; ;st-mem-0 v+s.
defb 0x02 ; ;delete .
defb 0x38 ; ;end-calc
call NEXT_LOOP ; routine NEXT-LOOP tests against limit.
ret c ; return if no more iterations possible.
ld hl,(0x5C68) ; find start of variable contents from MEM.
ld de,0x000F ; add 3*5 to
add hl,de ; address the looping line number
ld e,(hl) ; low byte to E
inc hl
ld d,(hl) ; high byte to D
inc hl ; address looping statement
ld h,(hl) ; and store in H
ex de,hl ; swap registers
jp GO_TO_2 ; exit via GO-TO-2 to execute another loop.
; ---
;; REPORT-1
REPORT_1:
rst 0x08 ; ERROR-1
defb 0x00 ; Error Report: NEXT without FOR
; -----------------
; Perform NEXT loop
; -----------------
; This routine is called from the FOR command to test for an initial
; iteration and from the NEXT command to test for all subsequent iterations.
; the system variable MEM addresses the variable's contents which, in the
; latter case, have had the step, possibly negative, added to the value.
;; NEXT-LOOP
NEXT_LOOP:
rst 0x28 ; ; FP-CALC
defb 0xE1 ; ;get-mem-1 l.
defb 0xE0 ; ;get-mem-0 l,v.
defb 0xE2 ; ;get-mem-2 l,v,s.
defb 0x36 ; ;less-0 l,v,(1/0) negative step ?
defb 0x00 ; ;jump-true l,v.(1/0)
defb 0x02 ; ;to L1DE2, NEXT-1 if step negative
defb 0x01 ; ;exchange v,l.
;; NEXT-1
NEXT_1:
defb 0x03 ; ;subtract l-v OR v-l.
defb 0x37 ; ;greater-0 (1/0)
defb 0x00 ; ;jump-true .
defb 0x04 ; ;to L1DE9, NEXT-2 if no more iterations.
defb 0x38 ; ;end-calc .
and a ; clear carry flag signalling another loop.
ret ; return
; ---
;; NEXT-2
NEXT_2:
defb 0x38 ; ;end-calc .
scf ; set carry flag signalling looping exhausted.
ret ; return
; -------------------
; Handle READ command
; -------------------
; e.g. READ a, b$, c$(1000 TO 3000)
; A list of comma-separated variables is assigned from a list of
; comma-separated expressions.
; As it moves along the first list, the character address CH_ADD is stored
; in X_PTR while CH_ADD is used to read the second list.
;; READ-3
READ_3:
rst 0x20 ; NEXT-CHAR
; -> Entry point.
;; READ
READ:
call CLASS_01 ; routine CLASS-01 checks variable.
call SYNTAX_Z ; routine SYNTAX-Z
jr z,READ_2 ; forward to READ-2 if checking syntax
rst 0x18 ; GET-CHAR
ld (0x5C5F),hl ; save character position in X_PTR.
ld hl,(0x5C57) ; load HL with Data Address DATADD, which is
; the start of the program or the address
; after the last expression that was read or
; the address of the line number of the
; last RESTORE command.
ld a,(hl) ; fetch character
cp 0x2C ; is it a comma ?
jr z,READ_1 ; forward to READ-1 if so.
; else all data in this statement has been read so look for next DATA token
ld e,0xE4 ; token 'DATA'
call LOOK_PROG ; routine LOOK-PROG
jr nc,READ_1 ; forward to READ-1 if DATA found
; else report the error.
;; REPORT-E
REPORT_E:
rst 0x08 ; ERROR-1
defb 0x0D ; Error Report: Out of DATA
t/data/zx48_base.asm view on Meta::CPAN
; This is a unary operation, so on entry HL points to the last value and DE
; points to STKEND.
;; st-mem-xx
st_mem_xx:
push hl ; save the result pointer.
ex de,hl ; transfer to DE.
ld hl,(0x5C68) ; fetch MEM the base of memory area.
call LOC_MEM ; routine LOC-MEM sets HL to the destination.
ex de,hl ; swap - HL is start, DE is destination.
call MOVE_FP ; routine MOVE-FP.
; note. a short ld bc,5; ldir
; the embedded memory check is not required
; so these instructions would be faster.
ex de,hl ; DE = STKEND
pop hl ; restore original result pointer
ret ; return.
; -------------------------
; THE 'EXCHANGE' SUBROUTINE
; -------------------------
; (offset: $01 'exchange')
; This routine swaps the last two values on the calculator stack.
; On entry, as always with binary operations,
; HL=first number, DE=second number
; On exit, HL=result, DE=stkend.
;; exchange
exchange:
ld b,0x05 ; there are five bytes to be swapped
; start of loop.
;; SWAP-BYTE
SWAP_BYTE:
ld a,(de) ; each byte of second
ld c,(hl) ; each byte of first
ex de,hl ; swap pointers
ld (de),a ; store each byte of first
ld (hl),c ; store each byte of second
inc hl ; advance both
inc de ; pointers.
djnz SWAP_BYTE ; loop back to SWAP-BYTE until all 5 done.
ex de,hl ; even up the exchanges so that DE addresses
; STKEND.
ret ; return.
; ------------------------------
; THE 'SERIES GENERATOR' ROUTINE
; ------------------------------
; (offset: $86 'series-06')
; (offset: $88 'series-08')
; (offset: $8C 'series-0C')
; The Spectrum uses Chebyshev polynomials to generate approximations for
; SIN, ATN, LN and EXP. These are named after the Russian mathematician
; Pafnuty Chebyshev, born in 1821, who did much pioneering work on numerical
; series. As far as calculators are concerned, Chebyshev polynomials have an
; advantage over other series, for example the Taylor series, as they can
; reach an approximation in just six iterations for SIN, eight for EXP and
; twelve for LN and ATN. The mechanics of the routine are interesting but
; for full treatment of how these are generated with demonstrations in
; Sinclair BASIC see "The Complete Spectrum ROM Disassembly" by Dr Ian Logan
; and Dr Frank O'Hara, published 1983 by Melbourne House.
;; series-xx
series_xx:
ld b,a ; parameter $00 - $1F to B counter
call GEN_ENT_1 ; routine GEN-ENT-1 is called.
; A recursive call to a special entry point
; in the calculator that puts the B register
; in the system variable BREG. The return
; address is the next location and where
; the calculator will expect its first
; instruction - now pointed to by HL'.
; The previous pointer to the series of
; five-byte numbers goes on the machine stack.
; The initialization phase.
defb 0x31 ; ;duplicate x,x
defb 0x0F ; ;addition x+x
defb 0xC0 ; ;st-mem-0 x+x
defb 0x02 ; ;delete .
defb 0xA0 ; ;stk-zero 0
defb 0xC2 ; ;st-mem-2 0
; a loop is now entered to perform the algebraic calculation for each of
; the numbers in the series
;; G-LOOP
G_LOOP:
defb 0x31 ; ;duplicate v,v.
defb 0xE0 ; ;get-mem-0 v,v,x+2
defb 0x04 ; ;multiply v,v*x+2
defb 0xE2 ; ;get-mem-2 v,v*x+2,v
defb 0xC1 ; ;st-mem-1
defb 0x03 ; ;subtract
defb 0x38 ; ;end-calc
; the previous pointer is fetched from the machine stack to H'L' where it
; addresses one of the numbers of the series following the series literal.
call stk_data ; routine STK-DATA is called directly to
; push a value and advance H'L'.
call GEN_ENT_2 ; routine GEN-ENT-2 recursively re-enters
; the calculator without disturbing
; system variable BREG
; H'L' value goes on the machine stack and is
; then loaded as usual with the next address.
defb 0x0F ; ;addition
defb 0x01 ; ;exchange
defb 0xC2 ; ;st-mem-2
defb 0x02 ; ;delete
defb 0x35 ; ;dec-jr-nz
defb 0xEE ; ;back to L3453, G-LOOP
; when the counted loop is complete the final subtraction yields the result
( run in 0.428 second using v1.01-cache-2.11-cpan-71847e10f99 )