Tranz Am: Routine at 6C96

6C96: Print Character

Used by the routines at PrintStringColour, DrawPlayArea and Score_Player.

Input
A	ASCII value to print
HL	Screen address

PrintScreen

6C96

PUSH BC

Stash BC, DE and HL on the stack.

6C97

PUSH DE

6C98

PUSH HL

6C99

LD L,A

Create an offset in HL.

6C9A

LD H,$00

6C9C

ADD HL,HL

Calculate offset for ASCII character (HL=HL * 8).

6C9D

ADD HL,HL

6C9E

ADD HL,HL

6C9F

LD DE,($5C36)

DE=CHARS.

6CA3

ADD HL,DE

DE=HL + 3C00. For examples of usage;

Letter	ASCII Value	* 8 (offset)	CHARS + offset
"U"	55	02A8	3EA8
"L"	4C	0260	3E60
"T"	54	02A0	3EA0
"I"	49	0248	3E48
"M"	4D	0268	3E68
"A"	41	0208	3E08
"T"	54	02A0	3EA0
"E"	45	0228	3E28

6CA4

EX DE,HL

Print the character to the screen.

6CA5

POP HL

Restore HL, containing the screen buffer location, from the stack.

6CA6

LD B,$08

B=08 (08 rows of pixels).

PrintScreen_Loop

6CA8

LD A,(DE)

Copy a byte from the font data to the screen buffer.

6CA9

LD (HL),A

6CAA

INC DE

Increment the font data by one.

6CAB

INC H

Move onto the next pixel line.

6CAC

DJNZ PrintScreen_Loop

Decrease counter by one and loop back to PrintScreen_Loop until counter is zero.

6CAE

POP DE

Restore DE and BC from the stack.

6CAF

POP BC

Reset HL and move to the next column, ready to print the next character.

6CB0

LD A,H

H=H - 08 (reset the display line).

6CB1

SUB $08

6CB3

LD H,A

6CB4

INC L

Increment screen column by one.

6CB5

RET

Return.

View the equivalent code in;