Product specifications

;into the write to VRAM output
;register
LD DE,960 ;Loop counter = 960
TEXMO2: CALL VDOUTP ;Output fill screen byte to screen
DEC DE ;Decrement loop counter and if
LD A,D ;loop counter <> 0 then goto TEXMO2
OR E ;else drop through to TEXMO3
JR NZ,TEXMO2
TEXMO3: LD A,255 ;Reset fill screen byte to 255
LD (FILTEX),A
TEXMO4: (End of routine)
Listed below is a section of code which demonstrates the use of the above routine.
It is assumed that the pattern generator library has been loaded with a series of ASCII
patterns for text mode use.
;
SAMPLE: LD A,’O’ ;Fill text screen with the symbol
LD (FILTEX),A ;’O’
LD A, ‘X’ ;Then fill text screen with the
LD (FILTEX),A ;symbol ‘X’
JR SAMPLE ;Then goto sample and do it again
;The update will occur so smoothly
;that these two characters will
;merge to form a ???? (diagram).
It is a simple matter and very convenient from a programming point of view to be able
to perform sprite collision detection routines under VDP interrupt.
The section of code listed below has been designed so that you have the option of
enabling the test or disabling the test through a variable called IONOFF (Impact
On/OFF) :
When IONOFF = 0 - No action taken
IONOFF = 1 - Impact test routine takes place
More important however, is the fact that it is now not necessary to keep repeatedly
calling the impact routine from within your main code but only to look at a single
variable TRUFAL:
When TRUFAL = 0 – No impact has taken place
TRUFAL = 1 – Then sprite impact has taken place
The sprite impact detection routine is that described in section 4.4. It is important to
note that if you are going to use this routine and because of the amount of time each
sprite impact test takes, you are constrained to a maximum number of ???? sprites
which you must not exceed.
It is assumed that a sprite attribute table delimeter has already been set up prior to
setting up the interrupt routine using the BLKSPR routine also described in section 4.