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<1234567…34>
  • Who has an Issue 1 or Issue 2 Spectrum??Do you have an Issue 1 or 2 Spectrum (ie machines with 5C102E and 5C112E ULA's) ??? I'm doing a lot of research into the ULA and also the reasoning …

    ... high impedance - this is a memory refresh issue.

    Tracking down ...
    csmith csmith November 2007 Games
  • ULA snow effectIt's wintertime, you know. [quote="http://ramsoft.bbk.org.omegahg.com/floatingbus.html"]when the I register falls in the range 0x40-0x7F then the UL…

    ... ULA gets confused by the memory refresh cycles of the Z80 (performed ... CPU interferes with the video memory address generated by the ULA ... the data from an unexpected memory location (which still belongs to ... does not read the video memory, so it leaves the bus ...
    Hikaru Hikaru January 2014 Development
  • 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…

    ... /> From Z80 Manual
    [quote]Memory Refresh (R) Register.

    ... The Z80 CPU contains a memory refresh counter, enabling dynamic memories to ... /> The data in the refresh counter is sent out on ... bus along with a refresh control signal while the ...
    RMartins RMartins June 2016 Emulators
  • Cobra - scrollingHi everyone, I have been studying some of the code in Ocean' Cobra game using a debugger, in the hope of improving my own scrolling routines. In cas…

    It seems logical enough - the memory refresh signal is probably linked to everything else, providing another way of getting a timing sync.
    cyborg cyborg October 2004 Development
  • InterruptsCan someone help with providing some info or a link about IM 2. I know I need to create a vector table and want to store this as high in memory as po…

    ... store this as high in memory as possible to keep it ... the table is in contended memory, some Spectrum models will show ... display. This is because during memory refresh the z80 puts IR (I ... into thinking there is a memory contention whem there is not ...
    Alcoholics Anonymous Alcoholics Anonymous February 2005 Development
  • Sprite adviceHello. So, I'm slowly getting to grips with Z80 assembly - currently equal parts frustration and enjoyment. Now looking for some advice to help shift…

    ... grab a number from the memory refresh counter. Only problem is that ...
    48K 48K May 2006 Development
  • Sprite adviceHello. So, I'm slowly getting to grips with Z80 assembly - currently equal parts frustration and enjoyment. Now looking for some advice to help shift…

    ... grab a number from the memory refresh counter. Only problem is that ...
    Alcoholics Anonymous Alcoholics Anonymous May 2006 Development
  • The New SPIN releases ThreadOk, as I'm now working on SPIN again full-time, and as a very wise man once said, "Release Early, Release Often"[1]... I'm going to release new SPIN…

    Though think of the I register in the $40-$7f range, the R register and memory refresh cycles :)
    This is only my first attempt at controlling an effect that's been known about for years!
    Woody Woody July 2006 Emulators
  • RealXThis may be a dumb question but will RealX ever get released?

    ... low byte, point at contended memory, shall be called a "snow ... ULA gets confused by the memory refresh cycles of the Z80 (performed ...
    Dunny Dunny July 2006 Emulators
  • RealXThis may be a dumb question but will RealX ever get released?

    ... ], but certainly not during the refresh cycle. And the sentence you ... ULA gets confused by the memory refresh cycles of the Z80 (performed ... ]
    ... explicitly refers to the refresh cycle, in fact. Seems like ...
    Luca Luca August 2006 Emulators
  • Spectrum 'slow down' hardwareAny one else got one of these ? If so do you find it useful ? [url]http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MESELX:IT&item=…

    ... for too long as the memory refresh is disabled, but mostly it ...
    Matt_B Matt_B October 2008 Hardware
  • Spectrum 'slow down' hardwareAny one else got one of these ? If so do you find it useful ? [url]http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MESELX:IT&item=…

    ... ) then the issue of DRAM refresh must have been addressed. My ... DMA transfer, i.e. steals memory cycles) rather than a ?hard ... will result in interrupting the memory refresh. Access by the ULA will ... continue to refresh the bottom 16K though, so ...
    Matt_B Matt_B October 2008 Hardware
  • Need help with interrupts againI'm fighting to understand how interrupts code handling works I'm trying to set my simple own interrupt routine, as I don't want to be dependent on …

    ... I to point into contended memory can cause snow in the ... on the address bus during memory refresh cycles which can fool the ...
    Alcoholics Anonymous Alcoholics Anonymous November 2009 Development
  • Games not compatible with real grey +2There are many threads about Spectrum+3/2A incompatibility issues but what about grey +2? I've found that games like Marauder and Skate Crazy don't w…

    ... values when reading from contended memory which causes rubbish to be ... one (during the auto-inserted memory refresh cycle) but I find it ...
    Alcoholics Anonymous Alcoholics Anonymous January 2010 Games
  • How works the Line-Draw ROM routine ?The 'complete spectrum rom dissasembly.pdf' show info related to the draw rom subroutine. The Line-Draw require two sets of parameters: X,Y coordinat…

    ... has special purpose (interrupt vector, memory refresh counter, command pointer, stack pointer ...
    Shiru Shiru June 2010 Sinclair Basic
  • Computing: the next 25 yearsWe saw the birth of the 8086 microprocessor which introduced Space Invaders to the arcades. Zilog Z80's microprocessor was released as a cheaper alte…

    ... supply voltage, more instructions, integrated memory refresh hardware) and was designed by ...
    Winston Winston July 2010 Chit chat
  • 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…

    ... also need to do the memory refresh too as the Z80 stops ...
    Winston Winston December 2010 Hardware
  • z80 Startuphi everyone, does the z80 upon start up reset all registers (including A) to 0? Many thanks, Robin

    Higher memory is not being accessed but you may be seeing memory refresh cycles which occur after every opcode fetch. That has the address IR (I register, R register) placed on the bus.
    Alcoholics Anonymous Alcoholics Anonymous August 2011 Hardware
  • Robocop 3 and Spectrum 128K toast-rackHi all, we are going on with the tests on the new 128K emulator for the V6Z80p board, and we have found something odd: Robocop 3 (designed for the 12…

    ... be a interference with dynamic memory refresh but.. who knows!!!
    zx81 zx81 June 2012 Emulators
  • ULA snow effectIt's wintertime, you know. [quote="http://ramsoft.bbk.org.omegahg.com/floatingbus.html"]when the I register falls in the range 0x40-0x7F then the UL…

    ... but

    [QUOTE]
    Memory refresh (R) is an 8-bit ... fetch and used for dynamic memory refresh. The 8th bit is not ... used for dynamic refresh. If necessary, the memory refresh register can be ...
    Basher Basher January 2014 Development
  • Address bus contents (i.e. PC) during execution of HALTI'm wondering if anyone can tell me what's placed on the address bus during execution of HALT, beyond the initial M1 cycle. The Z80 user manual state…

    ... the answer, though, in that memory refresh still occurs, and the value ... entropy and executes from contended memory, incorrect emulation of this would ...
    zub zub April 2014 Hardware
  • Favourite Speecy HardwareHi, Just wondering what your favourite piece of Spectrum add-on hardware is/was? How about the Alphacom thermal printer? Or the Currah Speach thin…

    ... first unit had a faulty memory refresh, but the replacement gave years ...
    Matt_B Matt_B January 2015 Sinclair Miscellaneous
  • HALT: Why always 4ts?Instruction breakdown of halt is like that: PC 4ts. That means it fetches instruction byte from ram which tooks 4 ts and then does nothing and read…

    ... : repeated memory reads). Or does it perform refresh cycles only ... , without actually reading the memory.
    memory refresh signals active.[/QUOTE]
    refresh etc is the same ...
    RetroTechie RetroTechie February 2015 Development
  • The I register and IM 1Hi al! I've been doing some coding, replacing the BASIC ROM with my own code and upon examination of a few 16Kb cartridges, all the ones I've look…

    ... they do.

    During refresh, the contents of the I ... when the CPU does a memory refresh cycle.

    [b][i ...
    1024MAK 1024MAK November 2015 Development
  • 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…

    ... a Z80 instruction fetch and memory refresh cycle.

    [img]https ... to be use as a memory chip select.

    I ...
    RMartins RMartins June 2016 Hardware
  • 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…

    ... cartridge logic to check refresh address, immediately followed by ... R register might wrack your memory refresh operation and crash ZX. ... of checked)
    2 - Refresh address being something like 00000000 ... .
    3 - Read Memory address equal to #0000
    RMartins RMartins June 2016 Hardware
<1234567…34>

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