Writing in EEPROM and reading by 6502

[GARTHWILSON]

There seems to be some quantitizing error making it hard to follow in the picture. It will make it easier if you put a little dead time between bytes.

[hitlp]

GARTHWILSON wrote:

There seems to be some quantitizing error making it hard to follow in the picture. It will make it easier if you put a little dead time between bytes.

How can I do this? Put a little dead time between bytes?

[GARTHWILSON]

The easiest would be to just put a delay loop between bytes as you send them, to take up enough time that you can clearly see the marking time in between, then see the start bit for each byte.

[BigEd]

I'd suggest you sample at least 4x faster - or post an image at least 4x wider, which is what I really mean. See the narrowest pulses? They have different widths in the image you posted, but in reality they must all be the same width. For anyone to figure out the bit boundaries, they need an idea of where bits start and end, so a bit more resolution would be helpful.

[BitWise]

hitlp wrote:

Hello guys. It's me again.

I came back with a new 6502 processor and by the time I communicated with the ACIA (6551) it worked correctly. Now I'm trying to do a serial output with "Hello World!". I'm trying to use Putty but I do not see anything in the text output. Using the logic analyzer, every time I press the 6502 reset, it "spits" the same output. But I can not analyze it.

What can it be now?

Check the cables, that you have the right serial port selected and the right baud rate.

You can check your serial port is working by looping TXD back to RXD and sending a few characters.

[hitlp]

Hello guys. It's me one more time.

I checked the cables, looped the TX and RX and I can receive the sent characters correctly.

I'm using a baudrate of 9600. Below is the logical analysis of when I press some character on the keyboard. Look through the zero channel of the analyzer that nothing happens.

captura05.PNG (4.73 KiB) Viewed 548 times

Below the analyzer brings the result of when I press the reset. I tried to increase the resolution. See if you can see better this way. Because of the resolution of my notebook, I could not get a better print. NOTE: Images are not on the same time scale. The first catch event is very fast.

captura06.PNG (5.09 KiB) Viewed 548 times

[hitlp]

Folks! Good news.

It worked. The problem was in the ACIA baudrate. I use a 1.8432 MHz crystal connected to ACIA ports 6 and 7. Port 7 before was connected to a capacitor and it was on GND. I removed the capacitor and it worked. The baudrate of 9600 was accurate!

  : D: D: D: D: D

A long time ago I was not so happy to see a Hello World! on my screen!

I'll send more news. Thank you all!!!

[BigEd]

(You found your problem while I was composing this - I made a mistake at first and got nonsense, but corrected myself and now it shows that it is possible to decode serial data manually.)

Quote:

Great, so if you can mock up a grid to show each bit time, or pair of bit times, and align it so you can mark off sets of ten bit-times, can you arrange that so you see a zero start bit then 8 data bits then a one stop bit? I think you probably can, and that's encouraging.

I think I see these pulse widths:

Code: Select all

412111 11112211 321211 321211 141211 6121 13111111 141211 212311 321211 312211 11...

which is

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0  0001 0010  1
0  1010 0110  1
0  0011 0110  1
0  0011 0110  1
0  1111 0110  1
0  0000 0100  1
0  1110 1010  1
0  1111 0110  1

and so on...
which would be

Code: Select all

48 65 6C 6C 6F 20 57 6F...

which makes "Hello Wo..."