I usually do avoid arguments, however since it is my thread I feel somewhat obligated to give my 2 cents worth.

According to them, China continues to be the number one source of counterfeit parts, by a wide margin.
Sounds likely and I don't doubt it.

(Personally, I wouldn't single out China ...

Either ordering a larger amount of 65C02 from Mouser to make it worth the shipping cost, or keep trying my luck with the likes of eBay where I probably could get at best a non WDC CMOS version.
I will reiterate that you need to be very cautious about ordering a 65C02 from an eBay seller. Not ...

The reason for the minimum is that Digikey part is sourced from Rochester Electronics, an obsolete parts liquidator. In this instance, Digikey is acting as a reseller, not a distributor. All orders processed through Rochester incur relatively large minimums. Rochester is definitely not hobby ...

Mouser in Thailand (Bangkok) seems to have genuine WDC products.
Mouser also has 16C550 UARTs in PLCC package (not in DIP package).

Digikey in Thailand seems to have genuine TL16C550BN (Texas Instruments) UARTs from Rochester Electronics in DIP package,
but it looks like TI isn't manufacturing ...

Done that. Let's see if someone knows.

I summarize the many differences between the NMOS 6502 and the CMOS at http://wilsonminesco.com/NMOS-CMOSdif/ .

That's a very interesting one. Thanks.


I'm using an NMOS 6502 (just guess it's NMOS. it draws ~100mA, gets quite warm, it's sanded off and relabeled). Not sure if that makes any ...

Long story short replacing the 74HCT04 with a much slower but pin compatible CD40106 solved the problem and everything works just fine.

My theory here is that with the 74HCT04 \WR was probably pulled down way before the address I wanted to write to was stable.
Your theory may be correct and if so ...

Just want to post an update because I ran into more problems that I could however solve meanwhile and maybe my solutions help someone else in the future.

After having the UART up and running I wrote some nice functions (and therefore used JRE PHA PLA instructions) to send and receive characters and ...

However while going thru the boxes I did find a third 16550 and this one just works.
What was your source for the UARTs? If eBay, there is no telling what you were sold. Also, it could be the UART was damaged by ESD, which is always lurking during the cold months.

The 16550 are all salvaged from ...

I've got it working!!!

After checking the wiring and not finding anything wrong I went thru my IC boxes looking for some 74HCT replacements to just eliminate the possibility that one of them is faulty. I found some and replacing them didn't solve the problem either. However while going thru the ...

OK I tried to send only capital U's which gives me a reading of 1280Hz +- a few Hz jumping up and down on the TX pin using this loop:


LOOP:
LDA UART5 ; Fetch the control register.
AND #$20 ; Bit5 will be set to 1 if UART is ready to send.
BEQ LOOP

LDY #$55
STY UART0

JMP LOOP


I thought ...

Capital U is hexadecimal $55, binary 01010101.

It's been 20 years that I had tinkered with the 16550, and it wasn't 6502 related,
but to me it looks like your schematic and your code are supposed to work.

Would be nice if you could post photos of your hardware, maybe we are missing something ...

Sadly I don't have a Scope,
however #BAUDOUT reads 153600 Hz on the frequency counter which divided by 16 equals 9600 and therefore should be corerct.

I have a MAX232 connected to the 16550.
Im using a USB to TTL serial adapter (CP210x based) with another MAX232 hooked up to it. (So in this case it ...

This is the first 6502 project I've ever built and also the first time I'm using the 16550 UART.

I'm trying to initialize a 16550 and send characters 0 to 255 in an endless loop via a max232 to my PC.
I was expecting some unprintable characters and somewhere in between the whole ASCII char set ...