Welcome on board Marco..

Not sure that I understand your issue but there's a "bug" with the indirect JMP.

It works properly only if the low/high bytes of the pointing adress are on the same page.

JMP ($C0FF) will not fetch the effective jumping adress from $C100 but from $C000.

Correct, simple use it on zero page.. but ...

Hi,
to make double indirect jump the simplest way should be :

- call your code that calculate final address
- push computed final address into stack (in just order..)
- RTS (that return to pointed address)

Can the zeropage locations (or code location for that matter) be determined t assemble time, and/or is some kind of relocatable file format supported?

Hi fachat,
I just purchased the full version and did some quick tests; the generated code (from basic compiler) is relocatable and partially ...

I receive some replies from owner (see below) and downloaded demo from website; with demo is possible to start up to 60 complete session (but for only one hour each). Software seem be complete with right tools and facilities.


Hi Maurizio,
First of all, thank you for your interest in my software ...

As per object.. I am curious to know if already tested from a forum member..

..
Neil (pedantic mode = off)

(of course, there are encodings like biphase mark which are much more robust and don't give a hoot about baud rates, but I don't know of any hardware that encodes them; you need to roll your own.)

..or more simply use a quartz or a 0.5% resonator (or an active ...

The internal oscillator (on the '168/'328 and newer) is 8Mhz derived via an RC circuit and out of the factory its accuracy is +/- 10%. This is good enough for serial comms up to 9600 baud and maybe a bit faster.

As long as you can do the calibration, yes. The internal oscillator is generally ...

Ciao,
I agree with you that it is not a replacement for the 65C51, it couldn't be for many reasons other than those you mentioned, starting from the 8 bytes occupied..
On the other hand WDC also failed to make one compatible with the old 6551..

CS0 signal is active low to select base address for device access, pins 13-14 (BA0 - BA1) are used to select 4 "pseudo" registers; BA2 at pin 2 is a further addressing to allocate more 4 bytes for polling flags
check the datasheet again, the 65C51, similar to the 65C22, has 2 chip selects: CS0 ...

To avoid any error at 230Kbaud 18,432,000 Hz is the maximum clock below 20Mhz ; using oscillator insthead resonator should be possible to overclock AVR at 22,118,400 hz with zero error
interesting! i knew AVRs generate the baud rate internally, but i thought they just had a hardwired oscillator ...

... so what's the maximum CPU speed you can pair this with before you need to add wait states on the CPU side?
I'm also curious about the maximum CPU speed... TIA...

Michael,
I have in use this circuit with 65C02 that run at 1.832 Mhz ; I can estimate that - vhitout variation - should be ...

very interesting project!
sometimes i lie in bed and wonder what could've been if WDC were to release an updated 65C51 that not only fixes the hardware bug but also included hardware SPI and I2C master/slave functionality. then i'd actually buy one of those :lol:

day dreaming aside, i took a look ...

Very nice! I'll have a look as I am investigating a method to connect an atmel avr to a 6502 bus. We may have had the same ideas.

Can you attach screenshots of the schematics as well? I do have eagle, but not really handy eg on my phone now!

Thanks
André

André,
attachment of first post is in ...

The 6551 (faux) pinout is nice. Have you implemented serial buffers by any chance?\]

Yes Michael, but tx/rx buffers are on AVR side

p.s. my apology for colored drawings, next time I will put only B&W PDF/JPG here..