Hi!

I suspect you are not reading the verilog code correctly.

"load_reg" uses a non-blocking assignment (<=) inside an always @(posedge clk) block; making it a registered signal, stable throughout the clock cycle.
"write_register" uses a blocking assignment (=) inside an always @* block; making it ...

Hi!

This is great, another open source BASIC interpreter for the 6502 :-)

I made a minimal port to the Atari 8-bit, only including a "DOS" statement. IMHO, for this to be more useful, you should add (minimal) "SAVE" and "LOAD" statements.

I suppose the floating-point support is written by ...

Hi!

Adding to the above, for more details you can see page 45 of the Altirra Hardware manual, at https://www.virtualdub.org/downloads/Altirra%20Hardware%20Reference%20Manual.pdf, on "overlapping interrupts", that states:

Overlapping interrupts

...There are no issues with an overlapping IRQ ...

Adding to the above, for more details you can see page 45 of the Altirra Hardware manual, at https://www.virtualdub.org/downloads/Altirra%20Hardware%20Reference%20Manual.pdf, on "overlapping interrupts", that states:


Overlapping interrupts

It is possible for the 6502 to first begin executing ...

Hi!

It is in fact a lot easier to deal with BRK, you just have to see if the flags pushed to the stack has the B bit set.

There is a misunderstanding here about the BRK: the problem is not that the BRK is missed by an IRQ, it is that an NMI can mask a BRK instruction - the CPU jumps to the NMI ...

Hi!

It is great that you are testing this properly!

After the discussion about a 24-bit PRNG in this thread I got motivated to do a better job of making a 16-bit random number generator than some other recent efforts which I won't share!

I had been looking back on this other thread where a ...

Hi!

Just found this fast 24 bit PRNG algorithm by Wim Couwenberg:

lda a ; Operation 7 (with carry clear).
asl
eor b
sta b
rol ; Operation 9.
eor c
sta c
eor a ; Operation 5.
sta a
lda b ; Operation 15.
ror
eor c
sta c
eor b ; Operation 6.
sta b

For more details: https://wimcouwenberg.wordpress ...

Hi!

That seems to be a nice patch, but it assumes that the Y register can be stomped, which might need further investigation. SKO hinted at this in the initial post.
Yes, this is true.

I scanned the usage of the above code a little, and it is only used on "CLEAR", "NEW" and "RUN", and in each ...

Hi!

Hi everyone,

The issue is with the following code:


; flush stack and clear continue flag

LAB_1491
LDX #des_sk ; set descriptor stack pointer
STX next_s ; save descriptor stack pointer
PLA ; pull return address low byte
TAX ; copy return address low byte
PLA ; pull return address high ...

Hi!

Over the weekend, I found myself writing a routine to calculate "factor1*factor2+offset", a multiply-add, with X and Y 8 bit numbers, and P an 16 bit number. Some of the routines can be reworked to do this faster, I settled in the mult21 with adding only one "adc" at the end, for 20 bytes ...

Hi!

My small serial bootloader is now published on Github ( https://github.com/tius/tinyload65 ).


Great to see the optimized software serial code :)

In the "optimized tx_byte for bit 0" you can chop two bytes by using ASL instead of ADC:
sta _tmp ; 3
lda #_OUT_LO ; 2
sta SERIAL_TX_PORT ; 4 ...

Hi!

Does the port on the back of your device look like this, and it is labeled RS-232C?

If so, that's a serial port (sometimes called a COM port) and not a parallel port. The cabling is different for those ports and there indeed is a "crossover" cable available for that kind of port. That was my ...

The worst cases in the divide routine that I have presented occur, ironically enough, when the divisor is a power of two. And the worst of the worst occurs when the divisor is 1 and the dividend is 32767. This case requires almost 2000 cycles to produce the result. For this reason, it seems ...

Hello 0010 all,

Mea culpa, mea maxima etcetera, mentioning "printer" was my mistake (no Centronics connector to be seem within miles) !


The IEEE-1284 standard is not a "printer" standard, is a bi-directional parallel communication protocol between PC computers and other devices.

Did you read ...

Hi!

There is not enough grounds in the DB25 interface to cover all signals, so the IEEE 1284 standard simply reuses grounds, and the standard explicitly says that you need a 36pin connector at the peripheral side to get the full speed (of more than 2MB/s).

See https://www.ti.com/lit/an/scea013 ...