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; Development testbed for a decimal conversion routine
;
; * Outputs "NUM_AMOUNT" decimal numbers stored in "Numbers" as ASCII
; encoded digits to STDOUT.
; * As it is hardcoded 16-bit: Always five digits and trailing zeros are shown
; * Uses a straightforward "divide and modulo" approach and can handle numbers
; between 0 and 65535, i.e. the fact that the QNICE CPU works with signed
; numbers is ignored for the sake of having the full 16-bit range.
; * Originally developed for being used in demos/q-tris.asm for displaying
; current level, completed lines and score.
;
; Two subroutines can be extracted from this testbed:
; DIV_AND_MODULO: 16-bit integer division with modulo
; MAKE_DECIMAL: the actual decimal conversion routine
;
; done by sy2002 in February 2016
#include "../dist_kit/sysdef.asm"
#include "../dist_kit/monitor.def"
.ORG 0x8000
RBRA START, 1
NUM_AMOUNT .EQU 20
Numbers .DW 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
.DW 10, 100, 1000, 10000
.DW 32768, 32767, 32769
.DW 65534, 65535
.DW 23976
Result_Buffer .BLOCK 5
New_Line .ASCII_W "\n"
START MOVE NUM_AMOUNT, R0
MOVE Numbers, R1
MOVE New_Line, R2
MOVE 0x30, R3 ; R3 = 0x30 = ASCII "0"
MOVE 5, R4 ; R4 = hardcoded 5 digits
MOVE 1, R5 ; R5 = 1 (for looping)
NEXT_NUM MOVE @R1++, R8 ; retrieve current number
MOVE Result_Buffer, R9 ; store resulting digits in R9
RSUB MAKE_DECIMAL, 1 ; perform decimal conversion
MOVE R4, R6 ; R6 = 5 digits overall
NEXT_DIGIT MOVE @R9++, R8 ; retrieve digit
ADD R3, R8 ; ASCII conversion
SYSCALL(putc, 1) ; print one digit
SUB R5, R6 ; R6 - 1: all digits done?
RBRA NEXT_DIGIT, !Z ; no: next digit
MOVE R2, R8 ; newline on STDOUT
SYSCALL(puts, 1)
SUB R5, R0 ; R0 - 1: all numbers done?
RBRA NEXT_NUM, !Z
SYSCALL(exit, 1)
; ****************************************************************************
; MAKE_DECIMAL
; 16-bit decimal converter: Input a 16-bit number and receive a 5-element
; list of digits between 0 and 9. Highest decimal at the lowest
; memory address, unused leading decimals are filled with zero.
; No overflow or sanity checks are performed.
; performed.
; R8: 16-bit number
; R9: pointer to the 5-word list that will contain the decimal digits
; ****************************************************************************
MAKE_DECIMAL INCRB
MOVE R8, R6 ; preserve R8 & R9
MOVE R9, R7
MOVE 10, R4 ; R4 = 10
XOR R5, R5 ; R5 = 0
MOVE R9, R0 ; R0: points to result list
ADD 5, R0 ; lowest digit at end of list
_MD_LOOP MOVE R4, R9 ; divide by 10
RSUB DIV_AND_MODULO, 1 ; R8 = "shrinked" dividend
MOVE R9, @--R0 ; extract current digit place
CMP R5, R8 ; done?
RBRA _MD_LOOP, !Z ; no: next iteration
_MD_LEADING_0 CMP R7, R0 ; enough leading "0" there?
RBRA _MD_RET, Z ; yes: return
MOVE 0, @--R0 ; no: add a "0" digit
RBRA _MD_LEADING_0, 1
_MD_RET MOVE R6, R8 ; restore R8 & R9
MOVE R7, R9
DECRB
RET
; ****************************************************************************
; DIV_AND_MODULO
; 16-bit integer division including modulo.
; Ignores the sign of the dividend and the divisor.
; Division by zero yields to an endless loop.
; Input:
; R8: Dividend
; R9: Divisor
; Output:
; R8: Integer quotient
; R9: Modulo
; ****************************************************************************
DIV_AND_MODULO INCRB
XOR R0, R0 ; R0 = 0
CMP R0, R8 ; 0 divided by x = 0 ...
RBRA _DAM_START, !Z
MOVE R0, R9 ; ... and the modulo is 0, too
RBRA _DAM_RET, 1
_DAM_START MOVE R9, R1 ; R1: divisor
MOVE R8, R9 ; R9: modulo
MOVE 1, R2 ; R2 is 1 for speeding up
XOR R8, R8 ; R8: resulting int quotient
_DAM_LOOP ADD R2, R8 ; calculate quotient
SUB R1, R9 ; division by repeated sub.
RBRA _DAM_COR_OFS, V ; wrap around: correct offset
CMP R0, R9
RBRA _DAM_RET, Z ; zero: done and return
RBRA _DAM_LOOP, 1
; correct the values, as we did add 1 one time too much to the
; quotient and subtracted the divisor one time too much from
; the modulo for the sake of having a maxium tight inner loop
_DAM_COR_OFS SUB R2, R8
ADD R1, R9
_DAM_RET DECRB
RET
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