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Question on Z80 R/W cycles.Snipped from the complete spectrum ROM disassembly: [CODE] Now the memory is checked. 11DA RAM-CHECK LD H,D Transfer the value…
... decreases it. I presume the zero flag is set then, before the ... re-read again and the zero flag set accordingly.
I ... test that the memory holds zero after it is decremented ? it ... -
Question on Z80 R/W cycles.Snipped from the complete spectrum ROM disassembly: [CODE] Now the memory is checked. 11DA RAM-CHECK LD H,D Transfer the value…
... ) will fail to set the zero flag, because it'll be decrementing ... -
Easy Compare On 2 Byte Register?e.g. HL, BC, DE Has anybody got a really easy way of doing this without comparing each byte seperately? Any maths has no effect on the flags as far a…
XOR A ; Clear Carry flag and zero A
SBC HL,DE ; Compare HL and DE
OR H
OR L
JP Z,match ; Zero flag will be set if HL=DE -
Easy Compare On 2 Byte Register?e.g. HL, BC, DE Has anybody got a really easy way of doing this without comparing each byte seperately? Any maths has no effect on the flags as far a…
... ;213114]XOR A ; Clear Carry flag and zero A
SBC HL ... L
JP Z,match ; Zero flag will be set if HL ... -
Whats Gone Wrong - Pixels Everywhere!Changed one small piece of code, that doesnt do anything to the screen and the following has happened: [img]http://www.officetrack.com/download/wos/…
... problem is unexpected carry or zero flag set on when increasing A ... -
Changing the colour of the loading 'stripes'I was wondering if it were possible to alter the default colours of the standard ROM loading 'stripes' via BASIC, mabye a POKE command of some descri…
... INC D This resets the zero flag..[/code]
11 instructions ... -
problem using FRAMES to generate 'random' numbersI realise the pros use bytes from ROM to get their random numbers, presumably because they want to use FRAMES to synchronise the printing and avoid s…
... as 'and 1' sets the zero flag. But why use jr nz ... -
problem using FRAMES to generate 'random' numbersI realise the pros use bytes from ROM to get their random numbers, presumably because they want to use FRAMES to synchronise the printing and avoid s…
... as 'and 1' sets the zero flag. But why use jr nz ... -
VIC 20 emulation on the SpectrumI'm sure most people are aware of the my attempt at bringing the full Commodore experience to Sinclair users with the "Twenty Commodes" program. It e…
... set from the mask? The zero flag should be set from (mem ... set either N or Z flag value, and decides by checking ... they only affect the Z flag there's almost no ... . The combined N/Z flag handling hasn't been a ... should only affect the Z flag. This doesn't seem ... -
VIC 20 emulation on the SpectrumI'm sure most people are aware of the my attempt at bringing the full Commodore experience to Sinclair users with the "Twenty Commodes" program. It e…
... set from the mask? The zero flag should be set from (mem ... -
VIC 20 emulation on the SpectrumI'm sure most people are aware of the my attempt at bringing the full Commodore experience to Sinclair users with the "Twenty Commodes" program. It e…
... of the instruction sets the zero flag if all set bits in ... give 00010010, which is not zero, so Z would be clear ... -
Interlace demoSorry to reference another thread like this, but in the thread: [url]http://www.worldofspectrum.org/forums/showthread.php?p=313428#post313428[/url] …
... the snapshot, open debugger, set zero flag, close the debugger and continue ... -
Machine code help pls: LDI example[deleted]
... instruction only sets/resets the zero flag according to the result of ... c later, to force the zero flag to consider the C register ... , which doesn't touch the zero flag either. (Or you can just ... -
Using INPUT without clearing last two lines of screen?I'm trying to print to the 22nd row of the screen using the ol' print #0 trick. Unfortunately, I require user INPUT which seems to wipe out the botto…
... Z flag when the BC register pair reaches zero, you ... OR will set the zero flag (because the result of ... operation will not set the zero flag.
Again, ... ; This tests whether A is zero
ret z
zero flag being set, so RET ... -
The F register unused bitsI'm doing some reading and trying to organize my Spectrum ML apprenticeship and while looking in greater detail at the flag register one question pop…
... F registers are carry and zero flag (maybe parity also can be ... -
Clearing the Carry flagI'm reading that sometimes I may want to clear the carry before using ADC or SBC. A simple AND A or OR B will do. However, as I see it, for 8-bit ar…
AND A changes the zero flag as well.
You ... specially to deal with carry flag.
SCF - set carry ... flag
CCF - change carry flag
There ... an instruction to unset carry flag but if you execute
Clearing the Carry flagI'm reading that sometimes I may want to clear the carry before using ADC or SBC. A simple AND A or OR B will do. However, as I see it, for 8-bit ar…
... , and A is zero, AND A will set the zero flag - and will ... to test whether A is zero. Even if you intend for ...Back to Skool disassemblyAs mentioned in [url="http://www.worldofspectrum.org/forums/showthread.php?t=22841"]this thread[/url], I've been working on a disassembly of Back to …
... ]
That's because the zero flag is set (by chance) upon ...What Z80 development tools do you use? What books?Hi. I've been meaning to do it for over 25 years, but.. better late than never :) I'm starting to learn machine code and am trying to get a developme…
...
and a ; is A zero?
ret z ; return if ... of an AND operation is zero, the zero flag gets set. So effectively ... test whether A is zero or non zero faster and with less ... 'll always get the result zero. Again, XOR A takes 1 ...What Z80 development tools do you use? What books?Hi. I've been meaning to do it for over 25 years, but.. better late than never :) I'm starting to learn machine code and am trying to get a developme…
... check the status of the zero flag, which seems a bit kludgy ...Obfuscated code ideaThe instructions [b]SUB A[/b] and [b]XOR A[/b] both have the effect of setting the accumulator to zero. The only difference between them is that [b]…
... forgot that when you have zero, the zero flag [I]isn't[/I ... ] zero.
[quote](my emulator ... use of the P/V flag.Z80 Machine Code Question...Hi Folks, I know not strictly a BASIC question but I have started to learn Z80 machine code - 25 years too late! :smile: I have been reading a book…
... operation doesn't affect the zero flag. Only the 8-bit operations ... , and that would set the zero flag. But there are more efficient ...IF and control flow in machine codeHi everyone, Basic has a nice control flow like if statements. How can these be done in machine code since i cant find anything thanks
IF and control flow in machine codeHi everyone, Basic has a nice control flow like if statements. How can these be done in machine code since i cant find anything thanks
... but will still set the zero flag if A=0. This is ... instruction will also set the zero flag if A=0 at the ...IF and control flow in machine codeHi everyone, Basic has a nice control flow like if statements. How can these be done in machine code since i cant find anything thanks
... but will still set the zero flag if A=0. This is ... instruction will also set the zero flag if A=0 at the ...Optimization for this codeHello, I have done and submitted a small program for the CSS Crap Game Compo which involves a machine code routine. The z80 with BASIC and MC is av…
... ]inc (hl)[/B] sets the zero flag and if [B]ld (hl ...Optimization for this codeHello, I have done and submitted a small program for the CSS Crap Game Compo which involves a machine code routine. The z80 with BASIC and MC is av…
... ]inc (hl)[/B] sets the zero flag and if [B]ld (hl ...
