PUSH HL
(C) SATSOFT PHN 270-72-36
Today I continued HEADINGS Codenamed 'PUSH HL' and
Bring to your attention a very simple procedure for deriving
POINT ON THE SCREEN:
; OUT POINT
ORG 40000
LD D, 10; x coordinate
LD E, 11, Y coordinate
LD A, # AF; CALCULATION OF ADDRESSES TO COORDINATES
SUB E
RET C
LD E, A
AND A
RRA
SCF
RRA
AND A
RRA
XOR E
AND # F8
XOR E
LD H, A
LD A, D
RLCA
RLCA
RLCA
XOR E
AND # C7
XOR E
RLCA
RLCA
LD L, A
Now we know the Segment number, series, columns and LINES. ALL
OF THESE Data stored in the register pair 'HL'. TK THIS LINE IN
Familiarity has 8 pixels, and SHOULD INCLUDE ONLY ONE
, SO SHOULD GET ANY BIT want to include.
In fact, his number is determined by the modulo
COORDINATES FOR X 8, A computes this balance - BY
MASKING OF FIVE bits. But the fact that the coordinates X
CHANGES LEFT TO RIGHT, IE 0,1,2,3 ,..., 175, and the number of
bits in Bytes FOUND APPROPRIATE LINE GOING THE OTHER WAY, IE
7,6,5 ,..., 0.POETOMU TO DO CONVERSION. IN CASE 'A'
Enter a number '# FE' (11.11111 million), and then make ROTATION
This byte N +1 times, where N - Modulo X ON 8.
LD A, D; x coordinate
AND # 07; MASKING
LD B, A; remainder of dividing x by 8
INC B; +1
LD A, # FE; PUT BYTE 11111110
LOOP RRCA; ROTATION N +1 TIMES
DJNZ LOOP
LD B, # FF; INVERSION TO SEAL POINT WAS BLACK
XOR B; ON WHITE
LD B, A; REMEMBER IN CASE 'B'
LD A, (HL); B 'A' in Georgia VALUE OF SCREEN
OR B; including the required BIT
LD (HL), A; GEORGIA SCREEN RESULTS
RET; OUT OF PROCEDURE:)
Command instead of 'OR B' CAN BE USED 'XOR B' AND SEAL TO BE
PERFORMED BY XOR'U. The idea is, everything should be
understandable, since PROGRAM IS VERY SIMPLE AND TO HER IN
ADDITION providing extra Number of comments.
WRITE ABOUT ALL THAT YOU ARE INTERESTED TO assembler SOUND
PREDELAH.PRISYLAYTE their programs, and I'll definitely (!)
Publish.
