Scrolling Tiles

[britlion]

Some ideas

Is

Code:

RL (HL)

At 15 T states

A better choice than:

Code:

LD A,(HL)
RLA
LD (HL),A

At 7+4+7=18 T states perhaps? (Also 1 byte shorter, and doesn't mess up your A register, for what it's worth - which is usually the biggest reason it's useful).


Similarly:

Code:

LD A,31
LD L,A
LD A,(__LABEL__bit0)

You are faffing with A, where:

Code:

LD L,31
LD A,(__LABEL__bit0)

is more direct, surely?


I suspect that:

Code:

LD A,(HL)
OR 1
LD (HL),A

Again faffs with the A register (for 7+4+7 T states), where

Code:

SET 0, (HL)

Is 15 T states and doesn't faff with the A register.

Code:

LD A,(__LABEL__bit0)
CP 0
JP Z,dontset0

CP 0 works, but is two bytes. You can trigger the flags with something like AND A - which is a single byte opcode, and faster.

Code:

LD A,(__LABEL__bit0)
AND A
JP Z,dontset0

Finally, I get the feeling that using a bunch of bytes in memory for the bit counter could be optimized by using bits of a byte for the bit information. But I'm way too distracted to try to refactor that right now So I'll stick to simple tweak suggestions.


Al that said. Wow. You're using assembler, and it's working like a charm! Well done! This isn't easy stuff