... m trying to replace a bit in a byte as follows, but having ... I want.

A=00 if bit to replace ...
(HL) is the target byte to have the bit (E ... as per the contents of A

Hope ... XOR (HL)
LD (HL),A

nearly does it ...

... and assembling the bits into a byte. I came up with this ... code:
IN A, (C) ; read port FFFE, 12 ... the compare works; is that a fair assumption? Are there systems ... something else? Also is there a way to speed this up ...

... !) decided to write something a) for 48k speccy b) ... I knew beforehand was a) the speccy screen memory ... that I created was a routine that draws 16x16 ... thing was to create a keyboard and joystick routines. ... that when called populates a byte in memory with bits ...

... which I bought in a job lot a few years back, ... trouble turning them at a near-constant speed. So ... directed into a WAV recorder, i.e. a laptop with ... screen, there's a byte extra or a byte missing here and there ... surprise surprise, that's a 50 Hz mains signal, ...

... per pixel, making up one byte per row. Because SpecBAS ... uses one [i]byte[/i] per pixel, we need ... 't - they use 1 byte per row, SpecBAS uses 8 ... we do that by reading a byte, and then extracting each ... each BIT and not each BYTE, we need to store ...

... AticAtac disassembly, evolving it into a much more documented assembly with ... SNA which is a byte-for-byte match to a reference SNA (game ... distributable and I'm assuming a disassembly of the game will ... br />
PS: There is a disassembly out there on the ...

Hi Guys

Just a quick question regards what the ULA is doing as its drawing each scan line. Assuming the beam has finished drawing the border, am I correct assuming its reading a byte of screen ram then an attribute byte, and so on...?

... look at loading schemes again (a subject that interests me). < ... don't fit nicely into a byte).

Also, did ... unpacking (as opposed to unpacking a compressed block had completed loading ... bytes could be achievable with a "normal" loading speed and ...

... and fast, down to a byte sized number A with the same remainder ... A,$40 with INC A before the shifts to save one byte if A ... $FF.
A=$FF overflows to ... saves one shift and one byte for a 19 bytes (74cc) snippet ...

... br />
The byte is a standard length of bits ( ... Now single registers are a byte in size and hence ... the second register of a pair stores the digits ... bit in a single register now represents a number 256 ... confound you) and use a compiler for that whilst ...

... 't have a large enough buffer(ie 1 byte) to receive ... Interface 1 uses to receive a byte from the RS232 port ... SER_FL
ld a,(hl)
and a
jp z ... /> inc hl
ld a,(hl)
scf
...

... is the first bit in a byte (i.e. bit 7); we ... '
......ld a,(hl) ;again we prepare the forcing byte
......rra ...
......ld c,a
......ex ...

... supper. I was thinking of a byte-wise method after building this ... If however you can find a shorter code, then I am ... /> INC HL
LD A,(HL)
RST #10
LD A,(HL)
INC DE
CALL #22B1
LD A,(HL)
RST #10

... a,(hl)
.....inc a ;test for #ff
.....jr nz,found0 ;byte ... is the first bit in a byte (i.e. bit 7); we ... /> .....ld (hl),a
.....inc hl ;move onto next byte
.....pop ... of the previous byte (in cy)
.....ld a,(hl)
.....djnz ...

... eachother - TZX being a more capable version of ... flavours of Speedlocks, used a "clicking" pilot tone - ... bits to a byte, so 16 flips per byte. The distance ... between the flips denoted a 1 or a ... br />
Creating a TZX from a WAV or VOC of ...

... " when the loader is INing a byte from the ear socket, and ...

... " when the loader is INing a byte from the ear socket, and ...

... or TAP format? Spin has a "save" option, but apparently snapshots ... up the TZX file from a snapshot data. But is it ... that will have a BASIC laoder, followed by a byte code dump with ... one wishes to make a TZX file from a snapshot even if ...

I've checked them on a byte-by-byte basis. The disk versions for 1986 and 1987 are *EXACTLY* the same ! I don't know whether it's supposed to be like this - I'll notify Andrew Barker as soon as possible.

... the ROM charset but have a lookup table containing the width ... />
Actually, it's probably a bit more involved. In each ... bits for each (and have a byte/entry).

Then to ... you'd need to do a bit of RR/RLing of ...

... I'm not talking of a faster or shorter method, ... just a method.period.

... carry flag to build up a byte in another register (say ... />
loop: (to shift A reg right 8 times)
shift A right
add carry ...

Java method to mirror a byte (from SPECSAISIE 1.3 - class ... />
public static byte reverseByte (byte in) {
byte out= 0;
for ...

... the same method extended to flip a word and an 8x8 character ...

... contexts in which I use byte-mirroring, my priority is ... Jet Set Willy), mirroring a byte is a very occasional operation, and ... />
For a game which involves much byte-mirroring during play ... , there may be a case ...

... entry should be disqualified on a technicality?[/quote]

Disqualification ... states nothing about executing on a spectrum, it's just Z80 ... words the entry must take a byte (0x00 - 0xFF) in any register ...

... way I know to mirror a byte is,

ld b ... b,(hl) 7T
ld a, 255 7T
sub b ... I only tested it on a few numbers. :)
What do ...

... if HL is pointing to a byte, INC H takes you down ... t hit the end of a character square or line).< ... times before we reach the byte we're using for ... character squares for the next byte.

Therefore the ... but if you play with a few simple examples it may ...

need a Table of 256 bytes stored on a 256byte boundary

on entry: a=byte to mirror

FlipByte:

ld h,TableAdress/256
ld l,a
ld a,(hl)
ret