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Canny use of the 'r' register?Seeing Sokurah's code in the [URL="http://www.worldofspectrum.org/forums/showthread.php?p=583188#post583188"]crunch sound thread[/URL] has made me th…
... about the r register.
I've used this a fair bit myself ... />
As it cycles irrespective of whether interupts enabled so presumably ... (though much much faster by the looks of it).
I ... see how it's a bit of a blunt instrument as ones ... -
The R RegisterI've found some documentation regarding the R register (in that it is updated every M cycle except for a certain number of opcodes in which it is upd…
... 've found some documentation regarding the R register (in that it is updated ... except for a certain number of opcodes in which it is ... only the lowest 7 bits". Does this mean that the maximum value of the R register is ... -
Emulator compatibility with real SpectrumHi emulator programmers... Having spotted for the last 6 months that my iPAQ is still missing a Spectrum emulator I started typing last tuesday - an…
... (Green Beret for one) use bit 7 of the R register as a flag.
Be ... s value. Bit 7 should only change with a "LD R,A" ... opcode.
Are you emulating the undocumented opcodes ... Flag affection is also one of the bigger issues which need special ... -
Beautifully programmed gamesJust watching the bobby bearing tzx and admiring the beautiful programming involved. Which other games would you say had asthetic programming opposed…
... the 'R' register in the 'sound routines' / 'wait for fly back'...
Bit 7 of the refresh 'R' register ... instead.
I use bit 7 of the 'R' register because you can test for ... -
Atic Atac speed.Dear all, Excuse the noob question, but does anyone know how fast Atic Atac runs at? What I mean is, frames per second, or the amount of pixels the…
Yes, bit 7 of the R register is used as an interrupt flag. And because LD A,R automatically sets the FLAG Register (you needn't test A at all) it's fast and ideal for sound loops. -
Adjusting your code for screen refreshingOk, I'm aware that I should know it already after writing 5 Spectrum games in machine code but interrupts and screen refreshes were always my weaker …
... do is set the interrupt handler to set bit 7 of the R register (see thread [url ... routine decrease a framecounter, setting bit 7 of R when it hits zero. In ... clear R.
In addition, instead of just waiting for bit 7 of R to ... -
R registerI'm cross-posting this as a spin-off of a [url="http://www.worldofspectrum.org/forums/discussion/52748/zx-spectrum-cartridges/p2"]thread in "Hardware…
... checking emulator support & correctness of the R register behaviour.
From Z80 ... , we know that:
1 - R register, bit 7 must not change without being ... sets R register to zero, hence also changes bit 7.
2 - R register is ... -
R Register, Contended RAM and ClonesHi. I've had a quick look at the CSS FAQ but didn't spot quite what I'm looking for (also the CSS FAQ doesn't have much detail of the clones - there …
... ) some code that relies on the progress of the R register. At one point I ... /> 1. What is the effect of contended RAM on the R-register? I do not ... Russian clone (Pentagon, Scorpion, ...) affect the R-register differently? Again I would guess ... -
Interrupts - been a while !Not sure if this is the right place for this (1st post on WOS, but been a speccy user since Dec'84 :-o (yes I am that old ! :p) ), But I can't for …
... a,0x80 ; flag the interrupt
ld r,a[/CODE]
What is the point/need ... . Again. You can use BIT 7 of the refresh register as a flag. It never ... !
LD A,R ; auto triggers the negative/positive flag and ... -
La Abadia Del Crimea - The definitive pollOn a scale of 1 to 10, vote on the score you think LADC deserves. Try and be honest at it while you can. ;) EDIT: This poll is effective for 2 week…
Hypersports had the 1st messing with the 'stack' to draw on the screen and 'pulling' graphic data using the stack and using bit 7 of the refresh register. Unless you know or earlier examples. LOL! -
La Abadia Del Crimea - The definitive pollOn a scale of 1 to 10, vote on the score you think LADC deserves. Try and be honest at it while you can. ;) EDIT: This poll is effective for 2 week…
[QUOTE=frobush;379278]Hypersports had the 1st messing with the 'stack' to draw ... on the screen and 'pulling' graphic data using the ... stack and using bit 7 of the refresh register. Unless you know ... -
Look whats possible in 924 bytesSo, finally after over a year of development and nearly 25 years since I first designed the graphics, I've actually made it to the point where this i…
... ,calc_no_inc ;if no bit 7 then process addition of data len
and ... /> ld a,ixl ;test bit 7 of the data register lo-byte to determine if ... -
Look whats possible in 924 bytesSo, finally after over a year of development and nearly 25 years since I first designed the graphics, I've actually made it to the point where this i…
... /> add a,a ;test bit 7 and x data length x ... ,calc_no_inc ;if no bit 7 then process addition of data len
... /> ld a,ixl ;test bit 7 of the data register lo-byte to determine if ... -
Look whats possible in 924 bytesSo, finally after over a year of development and nearly 25 years since I first designed the graphics, I've actually made it to the point where this i…
... ld a,ixl ;test bit 7 of the data register lo-byte to determine if ... ld a,ixl ;test bit 7 of the data register lo-byte to determine if ... in counter B first. The register is checked, and if ... -
Look whats possible in 924 bytesSo, finally after over a year of development and nearly 25 years since I first designed the graphics, I've actually made it to the point where this i…
... a,ixl ;test bit 7 of the data register lo-byte to determine ... ld a,ixl ;test bit 7 of the data register lo-byte
... />
Also the "test bit 7" comment naturally splits over ... -
Madness or inaccurate docs: RR r/RL r?According to the Z80 User's Manual, the instruction RR r/RL r should rotate the carry flag into bit 0 or bit 7 of the register in question (bit 0 or …
... the instruction RR r/RL r should rotate the carry flag into bit 0 or bit 7 of the register ... in question (bit ... 0 or bit 7 depending ... -
Madness or inaccurate docs: RR r/RL r?According to the Z80 User's Manual, the instruction RR r/RL r should rotate the carry flag into bit 0 or bit 7 of the register in question (bit 0 or …
... the instruction RR r/RL r should rotate the carry flag into bit 0 or bit 7 of the register ... in question (bit ... 0 or bit 7 depending ... -
The R RegisterI've found some documentation regarding the R register (in that it is updated every M cycle except for a certain number of opcodes in which it is upd…
Ignore Dr. Beep.
The low 7 bits of the R register act as a 7-bit counter. The high bit will stay set if you set it, and stay reset if you unset it. -
The R RegisterI've found some documentation regarding the R register (in that it is updated every M cycle except for a certain number of opcodes in which it is upd…
... />
The low 7 bits of the R register act as a 7-bit counter. The high bit will stay ... />
can you tell how the refresh works then?
I ... -
The R RegisterI've found some documentation regarding the R register (in that it is updated every M cycle except for a certain number of opcodes in which it is upd…
I can quote the FAQ, which says: "The highest bit of the R register is never changed: this ... is because in the old ... the chip the bits where grouped in a 128x128 matrix, needing a 7 bit ... -
Atic Atac speed.Dear all, Excuse the noob question, but does anyone know how fast Atic Atac runs at? What I mean is, frames per second, or the amount of pixels the…
... of the high bit of the 'r' register! :D[/QUOTE]
High bit of the R register? I thought the R register ... br /> (i.e. Bit 7 always 0). This is ... ve just read about the R register (it is paired ... writing a fixed value to the<… -
Atic Atac speed.Dear all, Excuse the noob question, but does anyone know how fast Atic Atac runs at? What I mean is, frames per second, or the amount of pixels the…
[QUOTE=BloodBaz;327520]
High bit of the R register? I thought the R register went up to 127 ... that you are right, unless bit 7 is manually set with a ... only the lower 7 bits are incremented as instructions are fetched, but bit 7 ... -
RET MHello. I?ve seen in the Joffa game SAUCER a kind of loop like this LOOP LD A,R RET M JR LOOP I do know what this loop mea…
... a rare bit of flicker but no slowdown, especially when the sounds are ... />
Is this R register routine the same but just toggling bit 7?
R or the cycling of the R register to affect the flags. -
ZX Spectrum CartridgesI have been thinking of "cloning" ZX Cartridges for a while (case, board and silicon skirt), to be able to make new releases or replace damaged cartr…
... checking emulator support & correctness of the R register behaviour.
From Z80 ... , we know that:
1 - R register, bit 7 must not change without being ... sets R register to zero, hence also changes bit 7.
2 - R register is ... -
Spectrum 48+ 4S - Upper RAM issue, and now a self-created problem!I recently picked up a known-flaky spectrum off eBay, to have a bit of fun fixing it and reliving youth. It was labelled as 'keyboard duff, shows…
... , the Z80 automatically outputs the contents of the R register and the I registers to the address ... low. R feeds A0 to A7, the contents of the I register goes to ... instruction, the Z80 increments the value held in the R register, except for bit 7, which ... -
Machine Code ChallengeHere's a challenge for all you Z80 programmers. Points to be awarded for elegance and brevity. (I haven't got the solution either) HL addresses the …
... of contiguous bytes in memory the number of bytes being held in the B register ... to ensure that the bit to the right of any bit that was ... that if bit 0 is set then bit 7 of the next byte ... br /> Also the very first bit encountered, i.e. bit 7 of initial HL, ... -
IN Port FE bit 6 confusionI know I've got this wrong. Tapes load fine but it all feels messy. Currently my emulator does this: Sets bit 6 of the result to 0. If (and only if…
... bit 6 of the result to 0.
If (and only if) bit 7 of the high ... byte of the ... address is 0 then bit 6 is ... -
Small ProblemI have a small problem (fnar!) that I'm trying to overcome. Basically I need to rlc or rrc bits 4 to 7 of the H register without touching the rest. …
... 7 of the H register without touching the rest. So bit 7 will shirt out and into bit ... 4 or the reverse bit ... 4 out into bit 7. Like doing ... -
ZXCF InterfaceI'm just trying to get an idea for the ZXCF interface, and to me, it looks a much cleaner design compared to divIDE (Of course, that's just my opinio…
... b0 of BLK0, Bit 3 is copied into b2 of SCRN and
bit 7 of the ... in the corresponding slot(s) and setting the R0 bit in the config register.
Another thing I've thought of ...
