Search found 347 matches

by leeeeee
Wed Jan 16, 2013 7:26 pm
Forum: General Discussions
Topic: STZ zp Opcode effect on various Retro-computers/consoles
Replies: 18
Views: 2514

Re: STZ zp Opcode effect on various Retro-computers/consoles

Faster, shorter, no decimal mode problems.

Code: Select all

1536: PHA
1537: LDA #2    ;color value
1539: STA 53272 ;store color register
1542: CLD       ;clear decimal mode
1545: ADC #2
1548: STA 1538  ;modify the code itself
1545: PLA
1546: RTI
Lee.
by leeeeee
Tue Dec 18, 2012 4:08 pm
Forum: Programming
Topic: .db directive
Replies: 11
Views: 14984

Re: .db directive

.db is define byte(s) and is followed by one or more byte sized constants.

Lee.
by leeeeee
Sat Dec 15, 2012 7:25 pm
Forum: Programming
Topic: Interrupt Handling
Replies: 29
Views: 3054

Re: Interrupt Handling

Quote:
So, I assume that since the interrupt bit was cleared when the interrupt fired (being an IRQ), that the restoration of the status register is what implicitly re-enables the interrupts for future interrupts.
Yes, that's exactly it.

Lee.
by leeeeee
Sun Dec 09, 2012 8:01 pm
Forum: Emulation and Simulation
Topic: Is this an overflow condition?
Replies: 14
Views: 2601

Re: Is this an overflow condition?

An overflow is only true when the carry from b6 to b7 and the carry out from b7 differ. As both carry bits are 1 in this case there is no overflow.

Lee.
by leeeeee
Sat Dec 08, 2012 11:43 pm
Forum: General Discussions
Topic: Building a simple 6502 microcomputer
Replies: 183
Views: 19563

Re: Building a simple 6502 microcomputer

I read somewhere that ROMs have to erased before writing. EEPROMs shouldn't need erasing before writing. You can erase the whole device in one go, having applied 12V to /OE and usually using a software code, but you don't need to.

You should be able to rewrite any or all of the bytes in a page in ...
by leeeeee
Tue Dec 04, 2012 2:26 pm
Forum: Hardware
Topic: OT: Why is DRAM faster than ROM?
Replies: 4
Views: 926

Re: OT: Why is DRAM faster than ROM?

I'm thinking of Amiga and 90s PC where there was an explicit copy of Kickstart/BIOS from ROM into RAM, for speed purposes. That was mostly because of the differing memory widths. PC BIOS ROMs were only 8 bits wide and Amiga kickstart was 16 bits wide so copying to 32 bit wide RAM could halve or ...
by leeeeee
Sat Dec 01, 2012 5:44 pm
Forum: Hardware
Topic: NINA - a homebuilt 6502 machine [video]
Replies: 20
Views: 2234

Re: NINA - a homebuilt 6502 machine [video]

It looks like he started with a slightly modified Micro UK101 and added bits.

I wonder how accessing the 6850 is handled, wait cycles?

Lee.
by leeeeee
Fri Nov 23, 2012 8:40 am
Forum: General Discussions
Topic: Translating russian CRT datasheet
Replies: 37
Views: 3741

Re: Russian

This page may be some use.

Lee
by leeeeee
Sat Nov 03, 2012 9:28 pm
Forum: Nostalgia
Topic: Compare the Z80 with the 6502...
Replies: 63
Views: 20566

Re: Compare the Z80 with the 6502...

Quote:
The address bus outputs the address, and the memory is read in the same cycle?
Yes, it is.
Quote:
I would really call this 2 cycles.
In that case I have two bridges you may be interested in.

Lee.
by leeeeee
Mon Aug 06, 2012 6:57 am
Forum: Nostalgia
Topic: Misc UK101 articles from Practical Electronics
Replies: 5
Views: 1294

Re: Misc UK101 articles from Practical Electronics

There's a whole lot more on that site if you start from here.

Lee.
by leeeeee
Sat Jul 28, 2012 1:50 pm
Forum: General Discussions
Topic: 2012 Olympics in London
Replies: 19
Views: 2011

Re: 2012 Olympics in London

But that is amazing you actually need translation for some!
Without subtitles the Red Riding Trilogy is aparently unpenetrable to some Americans and the US distributors for Attack the Block want(ed) to subtitle it.

I believe Gregory's Girl was also subtitled for US release.

Lastly, we do so love ...
by leeeeee
Sat Jul 28, 2012 11:08 am
Forum: General Discussions
Topic: 2012 Olympics in London
Replies: 19
Views: 2011

Re: 2012 Olympics in London

And I was wondering if Brits hate it when we try to put on their accent?
No, because there isn't a british accent, there are lots of them - some of which need subtitles when played to non british audiences.

The accent that you all try to do is the caricature british accent that's always used in ...
by leeeeee
Sun Jul 22, 2012 10:24 pm
Forum: Emulation and Simulation
Topic: Kowalski Simulator Macro Anomalies
Replies: 18
Views: 7643

Re: Kowalski Simulator Macro Anomalies

The latest version is 1.2.11
by leeeeee
Fri Jul 13, 2012 6:38 pm
Forum: Hardware
Topic: Trivial circuits for sbc
Replies: 74
Views: 8691

Re: Trivial circuits for sbc

Will the data be stored in the eeprom if i write pretending it was a static ram
No.

You start with by writing a write command.

You then write up to a page of data writing each byte within the maximum time from the last byte, usually 100us.

You then either wait for the maximum write time or poll ...
by leeeeee
Fri Jul 13, 2012 10:40 am
Forum: Hardware
Topic: Trivial circuits for sbc
Replies: 74
Views: 8691

Re: Trivial circuits for sbc

The busy bit, b6 at any address, will toggle between 0 and 1 on subsequent reads until a command is complete.

Lee.