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<1234567…34>
  • Contention: LDI vs LD (ss), rAccording c.s.s. FAQ: instruction LD (ss),r breakdowns as pc:4,[b]ss:3[/b] and LDI as pc:4,pc+1:4,hl:3,[b]de:3,de:1 x 2[/b] can anyone explain why …

    ... ]ss:3[/b]
    and LDI as pc:4,pc+1 ... explain why WRITE operation in LDI introduces two delays? or that ...
    Fikee Fikee February 2011 Development
  • Memory Map/ContentionHi I'm new to speccy coding (well I did some z80 coding a few years back - like 20yrs ago :) ), and I'd like to get back into writing some scrolling…

    ... a correct map for memory contention?

    Address Size Area ...
    ZJones ZJones September 2006 Development
  • I/O contention model questionHi everyone, Sorry for my poor english. Together with a friend we are working on ZX Spectrum 48k implemented in FPGA. We have found bug in the Spect…

    ... .s faq describing I/O contention.

    The 48k ... to lead to the following contention patterns:

    High ... /> in 40 - 7F? | Low bit | Contention pattern
    ------------+---------+-------------------
    No | Reset ...
    brian-82 brian-82 February 2007 Development
  • Contention and floating bus timingHello, I was recently playing a bit with memory contention and floating bus stuff in ZXDS and there is one thing which puzzles me a bit. It is the d…

    ... playing a bit with memory contention and floating bus stuff in ... sense it starts applying the contention a few cycles earlier, namely ...
    Patrik Rak Patrik Rak September 2007 Emulators
  • CPI emulationI'm currently writing Sinclairean's emulation assembly for the CPI/CPD/CPIR/CPDR instruction group. Does anybody know what exactly the behavior of th…

    ... [/B] cycle, just like the LDI/LDD/LDIR/LDDR group (!)
    contention.
    Madonna Mk 2 Madonna Mk 2 March 2010 Emulators
  • Contention detectionJust a thought, based on discussion elsewhere... Is there any way of telling if reads/writes are being contended around the time that they happen? L…

    ... whether the memory is in contention?
    joefish joefish April 2010 Development
  • 128K Contention - How to get it right?With my recent hardware hackery, I've built a 128K (toastrack) clone. I can't quite get the contention right though. What I'm lack is a clear descri…

    ... 0x7ffd, 0xbffd and 0x3ffd port contention behaviour.

    ... However, I find that contention is applied too often ... /> To correct the excessive contention, I replicated ULA14 and ULA15 ... someone describe accurately the contention behaviour for the 128K ...
    csmith csmith July 2011 Hardware
  • BIT b,(ii+n) contentionThe documentation says that BIT b,(ii+n) has this contention pattern: pc+1:4,pc+2:3,pc+3:3,pc+3:1 x 2,ii+n:3,ii+n:1 See [url]http://scratchpad.wiki…

    ... b,(ii+n) has this contention pattern:

    pc+1 ... Tstate.

    So the contention pattern should be:

    Oibaf Oibaf July 2012 Emulators
  • LDI questionWhen using LDI (or LDD) is it possible to access the value that is transfered from (HL) to (DE), or does the Z80 use an internal data cache to store …

    When using LDI (or LDD) is it possible to access the value that is transfered from (HL) to (DE), or does the Z80 use an internal data cache to store it?
    MatGubbins MatGubbins March 2014 Development
  • Understanding contentionI'm trying to understand contention and its implications when some "weird" bus cycles (such as I/O cycles with I/O addresses in the contended memory …

    I'm trying to understand contention and its implications when some ... both memory and I/O contention. Memory contention causes T1 to be ... ?

    Also: memory contention makes T1 to be enlarged ... for instance, to avoid memory contention) that begins at the ...
    mcleod_ideafix mcleod_ideafix May 2015 Hardware
  • Question of contentionI'm not desperate to go digging through technical descriptions in depth, but one thing bugs me about the Speccy's video contention model - and that's…

    ... about the Speccy's video contention model - and that's the ... /> And then there's the contention pattern where the memory is ... 16, so that means the contention pattern covers a run of ...
    joefish joefish January 2016 Hardware
  • 128K memory bank selection to avoid contention issuesI'm currently developing a game and I'm trying to get my head around the memory contention issues of the various 128K/+2/+2A/+3 spectrum models in or…

    ... my head around the memory contention issues of the various 128K ... what is the cause of contention for banks 1,3,4 ... downs due to this apparent contention issue.
    adrian_singh adrian_singh May 2017 Development
  • Memory Contention: A Hypothetical Fix?I have just had this crazy thought: If one were to wire an additional memory chip, say a 6264 8Kx8 SRAM, in parallel with the main memory so that it …

    ... reduce the effect of memory contention considerably. Possibly with the addition ...
    The_Bert The_Bert September 2017 Hardware
  • Writing own emulator: Contention questionsHi! (I don't know if this message should be here or in Hardware) I'm trying to write my own emulator just for the sake of it, and I'm having pr…

    ... having problems understanding the memory contention in 48k, in instructions like ... is being used there for contention.


    Thanks ...
    MrKii MrKii April 2018 Emulators
  • [Asm] Is this nested loop faster than LDIR or a bunch of unrolled LDI's?Hi all. I'm learning Z80 asm on Speccy 48K, and to start with I decided to write my own "CLS" routine (without relying on ROM calls or LDIR) as a lea…

    ... a partially unrolled set of LDI's (let's say 5 ...
    ST1 ST1 November 2018 Development
  • A few questions regarding EmuZwinI had posted this in the development forum and then remembered there was an emulators forum, so apologies for the repetition. 1. I have been trying …

    ... :03, dmsmith wrote:

    [LDI taking 24 Ts]

    contention.

    [quote]
    4 ...
    Woody Woody August 2004 Emulators
  • Fast screen writesI wondered what the faster than LDIR methods of writing to the screen were.

    ... get clobbered by the memory contention in the screen ram which ... delay. Using unrolled loops of LDI instructions gets around both of ... it no faster than the LDI method. That said, a lot ...
    Matt_B Matt_B October 2008 Development
  • Fast screen writesI wondered what the faster than LDIR methods of writing to the screen were.

    ... 16K will be clobbered by contention repeatedly, if it's repeatedly ... iteration. LDI only does it for three, which means some contention, but ...
    Matt_B Matt_B October 2008 Development
  • Brand new River Raid remake?one of my friend is trying to make a riverraid remake on flash just to have fun, I checked zx spectrum port of river raid. it is bad, really bad, jer…

    ... might as well use the LDI version. The PUSH one does ... these effects is how the contention actually makes them sychronise themselves ...
    joefish joefish May 2009 New game ideas
  • Which is the most technically accurate Spectrum Emulator?Ok, which is the most technically accurate Spectrum Emulator? Please don't just vote but give reasons why.

    ... ... failed (0xff)
    High port contention 1... failed (0xfe)
    High ... port contention 2... failed (0xfe)
    0xbffd ... /> BIT n,(IY+d)
    LDI
    LDD
    LDIR
    BIT n,(IY+d)
    LDI
    LDD
    LDIR
    rich_chandler rich_chandler June 2009 Emulators
  • Colour clash on the Commode64?Was there any? Every now and again, I see a screen shot like this... [img]http://www.lemon64.com/games/screenshots/full/j/jack_the_nipper_02.gif[/i…

    ... a lot more predictable) memory contention.[/QUOTE]

    Didn't ... -up', cycle wise - so that LDI was 4 t-states instead ...
    frobush frobush September 2009 Chit chat
  • LDIR timings in contended RAM?The 48K Spectrum technical reference page ([URL="http://www.worldofspectrum.org/faq/reference/48kreference.htm"]here[/URL]) describes the detailed ti…

    ... using chains of LDI instructions (e.g. 32 LDI instructions in a ... HALT you can reduce the contention.
    BloodBaz BloodBaz June 2010 Development
  • LDIR timings in contended RAM?The 48K Spectrum technical reference page ([URL="http://www.worldofspectrum.org/faq/reference/48kreference.htm"]here[/URL]) describes the detailed ti…

    ... :1, de:1" ie apply contention based on the value of ... , run for 1 tstate, apply contention for the value of DE ... ]ldi[/b], assuming there would be just one point of contention with ...
    ajmoss ajmoss June 2010 Development
  • Using the stack to copy memory blocksA [b]PUSH[/b] and a [b]POP[/b] instruction together take less time than two [b]LDI[/b], so long [b]POP/PUSH[/b] sequences are sometimes used to copy …

    ... largely comes down to memory contention. LDI has DE on the bus ... /> The quickest copy would use LDI during the uncontended part of ... kicks in, and back to LDI afterwards. Has anyone ever written ...
    Matt_B Matt_B August 2010 Development
  • Using the stack to copy memory blocksA [b]PUSH[/b] and a [b]POP[/b] instruction together take less time than two [b]LDI[/b], so long [b]POP/PUSH[/b] sequences are sometimes used to copy …

    ... ] uses it. I originally used LDI but could only manage to ... to synch themselves around the contention. This let me put a ...
    joefish joefish August 2010 Development
  • Recent talk of developing new SpectrumsHi all, I can see from a few threads on here that some Wossers like Vasil and Aien 8 are interested in developing more powerful Spectrums or improvi…

    ... fast an unrolled set of LDI instructions will run) but of ... gonna lose a lot to contention. Unless the CPU is fast ...
    Winston Winston December 2010 Hardware
  • Contention: LDI vs LD (ss), rAccording c.s.s. FAQ: instruction LD (ss),r breakdowns as pc:4,[b]ss:3[/b] and LDI as pc:4,pc+1:4,hl:3,[b]de:3,de:1 x 2[/b] can anyone explain why …

    ... ]ss:3[/b]
    and LDI as pc:4,pc+1 ... explain why WRITE operation in LDI introduces two delays?[/quote]
    contention pattern.
    Philip Kendall Philip Kendall February 2011 Development
  • Tile based graphics and scrolling thingy...Here's my best attempt so far at a tile based rendering and scrolling routine. It draws in 22 8*8 graphics tiles along the top of the screen (junk i…

    ... .org/faq/reference/48kreference.htm#Contention[/url], [url]http://www.worldofspectrum ... - im perhaps confusing you, the LDI scroll was used many times ...
    Fikee Fikee September 2011 Development
  • Fairlight's use of LDIRYS, comparing Fairlight and Nightshade, said: [quote]Fairlight is much more interesting even though the techniques that Bo Jangeborg uses for screen…

    ... byte (or more due to contention), LDI takes 16, and PUSH writes ... (or 16 when there's contention), but there's a big ...
    Metalbrain Metalbrain January 2012 Sinclair Miscellaneous
<1234567…34>

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Related Threads

  • Contention: LDI vs LD (ss), rAccording c.s.s. FAQ:<br /> <br /> instruction LD (ss),r breakdowns as pc:4,[b]ss:3[/b]<br /> and LDI as pc:4,pc+1:4,hl:3,[b]de:3,de:1 x 2[/b]<br /> …
  • Z80 cycle contentionHi,<br /> Does anybody knows exactly when the ula halts the Z80 clock during a memory r/w cycle?<br /> I mean which Z80 clock cycle, T1 or T2?<br /> …
  • Memory Map/ContentionHi <br /> I'm new to speccy coding (well I did some z80 coding a few years back - like 20yrs ago :) ), and I'd like to get back into writing some scr…
  • I/O contention model questionHi everyone,<br /> <br /> Sorry for my poor english. Together with a friend we are working on ZX<br /> Spectrum 48k implemented in FPGA. We have foun…
  • Contention and floating bus timingHello,<br /> <br /> I was recently playing a bit with memory contention and floating bus stuff in ZXDS and there is one thing which puzzles me a bit.…
  • Contention detectionJust a thought, based on discussion elsewhere...<br /> Is there any way of telling if reads/writes are being contended around the time that they happ…
  • 128K Contention - How to get it right?With my recent hardware hackery, I've built a 128K (toastrack) clone. I can't quite get the contention right though.<br /> <br /> What I'm lack is a …
  • 128K Contention - How to get it right?
  • BIT b,(ii+n) contentionThe documentation says that BIT b,(ii+n) has this contention pattern:<br /> <br /> pc+1:4,pc+2:3,pc+3:3,pc+3:1 x 2,ii+n:3,ii+n:1<br /> <br /> See [ur…

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