Product specifications

ADD HL, DE ;Add to relative address contained
;in HL to give true VRAM address
EX DE, HL ;of pattern generator byte to be
;examined – Result in DE
POP HL ;Retrieve old sprite X/Y coords
PUSH DE ;Save pattern generator byte
;address
LD A,H ;Perform bit test on extracted
AND 248 ;pattern generator byte
LD L,A ;using table BITTAB
LD H,0
LD DE,BITTAB
ADD HL,DE
LD A,(HL) ;Read byte from pattern generator
POP DE ;table
CALL VSETRD
CALL VDINPT
AND C ;If bit = 0 then exit routine
CP 0 ;Acc = 0
RET Z
LD A,1 ;If bit is < > then Acc = 1
RET ;Return to calling routine
Option 2
;
;DOT -SPRITE TO BACKGROUND MAPPING ROUTINE
;
; LOOK AT 12 POINTS WITHIN 16 6IMES 16 BIT SPRITE PATTERN
; AND RETURN THE CHARACTER VALUE UNDERNEATH THE
; SPRITE EXTRACTED FROM THE PATTERN NAME TABLE
; (DISPLAY SCREEN) AT EACH OF THESE POINTS IN SPRP1
; TO SPRP12
;
; RETURN THE PATTERN NAME TABLE (DISPLAY SCREEN)
; ADDRESSES OF THE FOUR CENTRE POINTS OF THE SPRITE
; PATTERN WITHIN THE LOCATIONS:
;
; CENLTL - CENTRE LOCATION TOP LEFT QUADRANT
; CENLTR - CENTRE LOCATION TOP RIGHT QUADRANT
; CENLBL - CENTRE LOCATION BOTTOM LEFT QUADRANT
; CENLBR - CENTRE LOCATION BOTTOM RIGHT QUADRANT
;
; REGISTER PAIR DE MUST CONTAIN THE VRAM START ADDRESS
; OF THE CONTROL BLOCK FOR THE SPRITE TO BE TESTED ON
; ENTRY
;
; THE SPRITE TO BE TESTED MUST BE ON-SCREEN WHEN DOT
; IS CALLED
;