It might be that its allowing the Zero page one as it might think you can/are using a ZP addressing mode which only needs 8 bits.

According to ca65 documentation I think this is why zero page 8-bit addressing is working here: https://cc65.github.io/doc/ca65.html#ss8.1

ca65 assigns each ...

Thank you Sean that's very helpful. I understand at a high-level.

I wonder if this is the same thing or same concept as the ld65 config segments: https://www.cc65.org/doc/ld65-5.html


For a bss type segment to be useful, it must be cleared somehow by your program (this happens usually in the ...

Thank you very much leepivonka and Gordon !
8-bit registers and 16-bit addresses ofcourse! I couldn't see the forest from the trees. Learning the hardware is one thing but then applying the hardware knowledge to programming is another (for beginners like me anyway).

And Gordon, thank you for the ...

Hi Guys, I'm trying to get the address of some of my variables.


.zeropage
ZPLoc: .res 20

.bss
BSSLoc: .res 10

.data
DataLoc: .res 15

lda #ZPLoc
lda #BSSLoc
lda #DataLoc


ld65 config file
ZP starts at $0000
RAM starts at $0200
where BSS is the first segment under RAM, and DATA is the ...

Hi guys,

I'm reading up on 65(C)02 assembly language and have started to look into the tools, i.e. assemblers, simulators, emulators...

There seems to be many tools and I'm kinda confused where to start:
http://6502.org/tools/

My daily driver is Linux. But I also use Windows in a virtual ...

Firefox6502, the circuit Enso posted is interesting, but you indicated you already have a 7805 and a heatsink. Not that you'll need much of a heatsink, but anyway... :)

I've edited your circuit, partly to correct the issues floobydust noted. It's helpful to clearly show *both* connections to the ...

Just out of curiosity, what is a 'raspberry pi 5.1V power supply'? I noticed at the raspi website a mention that one is required, but every device I've seen is powered by a usual 5V USB wallwart. I have a box of ones that claimed 2+ amps but were not providing that (as USB spec requires 500mA and ...

Unless I'm missing something, you have the battery and the Pi +5V supply coming in and going thru a pair of caps in parallel. Caps won't pass DC, so neither position of the switch will result in having +5V to power your circuit.
You are totally correct! Dumb mistake by me. I should have these caps ...

Hi guys,

Attached is my power circuit (pdf) designed from the information gathered within this thread.
I'd like to have a mobile 65C02 computer that I can take around with me. Size doesn't matter here (within reason).
What I'm trying to do is to have a circuit with two power sources, a Raspberry PI ...

Thank you very much Michael. I'm continuing to design and build.

The other factor for the 128k devices for rom is cost. Buying new, a 32k eeprom (28C256) will likely cost you at least 5x a 128k flash (39SF010). Having just had a look at Mouser there's very little differecne between their 32k and 128k static rams. Getting the larger size adds flexibility for ...

Thanks for the heads up BDD. I have read up on the 65C51 bug. In the last 2 weeks I had changed my mind several times on which way to go, use a: 65C51, or an NXP UART, or even implement SPI which will open up a world of other chips (including UARTs)!

Some history which will help show you where my ...

Thanks GARTHWILSON and BDD. I've now looked up the DC Characteristics of both the 65C51 and the FTDI chips:

65C51
VOH MIN 2.4v
VOL MAX 0.4v

FTDI TTL-232-5V
VOH MIN 3.2v
VOL MAX 0.6

FTDI TTL-232-3V3
VOH MIN 2.2v
VOL MAX 0.6

Also thanks BDD for the lesson in "how to teach a man to fish ...

I'm trying to do this also, and have been reading up. But I'm stuck on one question: what output voltages comes out of the 65C51 TxD, RxD, CTS, RTS pins? Is it 5v, 3.3v, TTL, RS-232?

The W65C51S manual doesn't answer this.

I ask as I'm about to buy one of these below but want to make sure it will ...

If you have SPI for other things already, one UART I have exercised (although not put to serious use yet), and like, is the MAX3100 :

small: 14-pin DIP or 16-pin QSOP or 24-"pin" (they're not really pins) TQFN
8-word transmit and receive buffers
has an IrDA mode as well
all common bit rates ...