Tests - ZX-Art

Search

Username:

Password:

Remember me

Register
I forgot password

РусскийEnglishEspañol

Comments
Graphics
Music
Mainpage
Stats
Authors
Parties
FAQ
Groups
Software

Demoscene
Games
System programs

Packers
Emulator
Programming

Assembler/Mcode
BASIC
General
Debuggers
Operating systems
Tests
Programming languages

Copy/Backup
Fonts/UDGs
Graphics
I/O Handling
Media Admin
Sound
Print
undetermined
Telecom/Network
Boot
General viewers

Misc
Covertape
Educational
Electronic Book
Compilation
Press
Applications
Art pack

Русский English Español

Gigascreen mode: Mix

Border: ON

Hidden pixels mode: OFF

Remember me

I forgot password

Search

Software System programs Programming Tests

Your very own ZX Spectrum radio

Latest comments

VBI: pop hl, dude :))

Apass: The image is very well done, however I have a gripe with the code snippet :P.
<joke>
I see 2 possibilities - 1) the code performs what it was intended to do but then is inefficient or 2) the code has a bug, and could be re-written in a simpler fashion.
First - the code copies in RAM at consecutive addresses the value of the accumulator, however, the accumulator is copied from the same memory location as DE is not incremented.
So the code can be simplified as:
PUSH HL
LD B, 4
LD DE, CODE
LD HL, #FE00
LD A,(DE)
LOAD LD (HL), A
INC HL
DJNZ LOAD
Note the position of the LOAD label. The only thing that this code does extra is wasting some time (7T states which is not easily replaced by NOPs)

Second - the code forgot to increment DE:
PUSH HL 11T states
LD B, 4 7T states
LD DE, CODE 10T states
LD HL, #FE00 10T states
LOAD LD A,(DE) 7T states
LD (HL), A 7T states
INC HL 6T states
INC DE 6T states
DJNZ LOAD 13/8T states
In this case, the code execution lasts 11 + 7 + 10 + 10 + 4 x (7 + 7 + 6 + 6) + 3 x 13 + 8 = 189T states.
If the code is re-written as:
PUSH HL 11T states
LD BC, 4 10T states
LD DE, #FE00 10T states
LD HL, CODE 10T states
LDIR 21/16T states
In this case, the code execution lasts 11 + 10 + 10 + 10 + 3 x 21 + 16 = 120T States
Or even quicker (with the observation that BC pair is not preserved)
PUSH HL 11T states
LD DE, #FE00 10T states
LD HL, CODE 10T states
LDI 16T states
LDI 16T states
LDI 16T states
LDI 16T states
This lasts 11 + 10 + 10 + 4 x 16 = 95T states (half of the initial variant)
</joke>

Finally, given the code snippet, I don't understand why the Z80 is dizzy?
If the code would have ended with:
DI
HALT
... On a Speccy... that would indeed make the CPU dizzy.
And it would have been quite a pun for the demoparty...

Shuran33: Крутой сборник и оболочка приятная! Спасибо

See all comments

Latest votes

devstratum	5	Ironman
ruguevara	5	Ironman
KOD	5	Ironman
Dimidrol	4	Skylnrmx
ufo.mesh	x	Ironman
Dimidrol	5	Ironman
Art-top	5	Ironman
Blogerator	5	Mystic Dragon
creator	5	Ironman
creator	5	balzamit

Developed by Artweb