[N8VEM: 17172] Toshiba 10mhz 82c55

[Jim Strickland]

I recently acquired a toshiba TMP82c55ap-10 in my quest to upgrade my zeta
to 20mhz. On replacing the existing 8255-5 with the 10mhz part, my zeta
will no longer initialize the parportprop. Is there anything special I'm
supposed to be doing with the newer CMOS part, such as having particular
downstream logic cmos (or faster)? I've buzzed out all the connections from
the back of the board to the pins. The system works normally when I go back
to the 8255-5. All this is without changing my zeta from its current 10mhz
clock speed My initial suspicion is that the new 82c55 is bad.

-JRS

[Sergey]

Apparently your TMP82C55AP is bad... you can try testing it somehow.

For CMOS 82C55 parts, I found the most reliable to be Intersil CP82C55A It
is rated to 8 MHz, but works nicely with 20 MHz Zeta. It is also currently
in production and available from Mouser, Avnet Express, and other
distributors.

While ago I bought a bunch of TMP82C55AP-10 from Utsource, and about 25% of
them were bad... so not much recommended.

Thanks,
Sergey

Post by Jim Strickland
I recently acquired a toshiba TMP82c55ap-10 in my quest to upgrade my zeta
to 20mhz. On replacing the existing 8255-5 with the 10mhz part, my zeta
will no longer initialize the parportprop. Is there anything special I'm
supposed to be doing with the newer CMOS part, such as having particular
downstream logic cmos (or faster)? I've buzzed out all the connections from
the back of the board to the pins. The system works normally when I go back
to the 8255-5. All this is without changing my zeta from its current 10mhz
clock speed My initial suspicion is that the new 82c55 is bad.
-JRS

[Jim Strickland]

Thanks. Good to know. I'll get the Intersil one from Mouser.

-JRS

Post by Sergey
Apparently your TMP82C55AP is bad... you can try testing it somehow.
For CMOS 82C55 parts, I found the most reliable to be Intersil CP82C55A It
is rated to 8 MHz, but works nicely with 20 MHz Zeta. It is also currently
in production and available from Mouser, Avnet Express, and other
distributors.
While ago I bought a bunch of TMP82C55AP-10 from Utsource, and about 25%
of them were bad... so not much recommended.
Thanks,
Sergey

Post by Jim Strickland
I recently acquired a toshiba TMP82c55ap-10 in my quest to upgrade my
zeta to 20mhz. On replacing the existing 8255-5 with the 10mhz part, my
zeta will no longer initialize the parportprop. Is there anything special
I'm supposed to be doing with the newer CMOS part, such as having
particular downstream logic cmos (or faster)? I've buzzed out all the
connections from the back of the board to the pins. The system works
normally when I go back to the 8255-5. All this is without changing my zeta
from its current 10mhz clock speed My initial suspicion is that the new
82c55 is bad.
-JRS

[Wayne Warthen]

I struggled with the Toshiba parts as well a while back. I have several of
the TMP82C55AP's and they all work well on my boards that are "mostly CMOS"
and do not work at all on my boards that are "mostly TTL". I came to the
conslusion that they are not TTL friendly.

I concur with Sergey that the Intersil parts work consistently well.

--Wayne

Post by Jim Strickland
Thanks. Good to know. I'll get the Intersil one from Mouser.
-JRS

Post by Sergey
Apparently your TMP82C55AP is bad... you can try testing it somehow.
For CMOS 82C55 parts, I found the most reliable to be Intersil CP82C55A
It is rated to 8 MHz, but works nicely with 20 MHz Zeta. It is also
currently in production and available from Mouser, Avnet Express, and other
distributors.
While ago I bought a bunch of TMP82C55AP-10 from Utsource, and about 25%
of them were bad... so not much recommended.
Thanks,
Sergey

Post by Jim Strickland
I recently acquired a toshiba TMP82c55ap-10 in my quest to upgrade my
zeta to 20mhz. On replacing the existing 8255-5 with the 10mhz part, my
zeta will no longer initialize the parportprop. Is there anything special
I'm supposed to be doing with the newer CMOS part, such as having
particular downstream logic cmos (or faster)? I've buzzed out all the
connections from the back of the board to the pins. The system works
normally when I go back to the 8255-5. All this is without changing my zeta
from its current 10mhz clock speed My initial suspicion is that the new
82c55 is bad.
-JRS