2 Sep
2023
2 Sep
'23
3:40 p.m.
On 2023-09-02 7:50 a.m., Peter Corlett via cctalk wrote:
On Fri, Sep 01, 2023 at 04:32:57PM -0600, ben via
cctalk wrote:
[...]
I need it simple, as I am bringing up a new cpu design. 36 bits lives
again*. Program testing is to be done I expect from the front panel,
until I get boot strap loader into eeprom. The 6850 is just right and
coding examples are easy to find. This last PCB is memory and IO.**
Ben.
* I am building one, if it works is is another story.
I use a lot of cmos pals in the design, it makes things so easy build
stuff with.
** Once working in need find N x 9 non volitile memory.
I think that way has been for a while. Having a
hard time finding a 68B50
on ebay. All the modern serial devices (I can buy) seem to be serial
interfaced. Sigh.
I see the 68B50 on AliExpress, and they're probably even genuine. The vendor
I'm tempted to order some other retro chips from offers them in five packs
for about a euro each.
For new parts available from a reputable supplier, there's the W65C51. The
bumph notes it is "compatible with 65xx and 68xx microprocessors". Available
in a variety of packages including DIP, and also in -S and -N variants
depending on whether you want CMOS or TTL levels, it runs at a nominal 5V
and has speed grades up to 14MHz. It's not a direct replacement for the 6850
but will look quite familiar and present no surprises. For new designs, it's
simpler to use as it doesn't need external baud rate generators.
A single W65C51N6TPG-14 (DIP, TTL, 14MHz) is €7.10 from my local Mouser.
If you can handle SMD, there's even the venerable 16550 and clones which
could be handy if you're trying to do high-speed serial, although that's got
a more 8080-style bus interface so you'll need a few extra gates to get that
going.