Z80 reset circuit

[jamma-plusser]

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some circuit
using TTLs and resistors, caps, etc, I simply want to buy an off the
shelf part which ONLY requires +5 volts, GND and a wire to connect it
to the reset line on my PCB. I don't want to have to wire up other
parts to it to get it to work.

Does such a modern part exist?

Thanks

 

[Rich Webb]

On Sat, 30 May 2009 22:25:19 GMT, jamma-plusser@hotmail.com
(jamma-plusser) wrote:

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some circuit
using TTLs and resistors, caps, etc, I simply want to buy an off the
shelf part which ONLY requires +5 volts, GND and a wire to connect it
to the reset line on my PCB. I don't want to have to wire up other
parts to it to get it to work.

Does such a modern part exist?

Do a search for "microcontroller supervisor". Microchip makes several
flavors, one of which will probably handle your needs.

--
Rich Webb Norfolk, VA

 

[Jon Kirwan]

On Sat, 30 May 2009 20:04:02 -0400, Rich Webb
<bbew.ar@mapson.nozirev.ten> wrote:

On Sat, 30 May 2009 22:25:19 GMT, jamma-plusser@hotmail.com
(jamma-plusser) wrote:

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some circuit
using TTLs and resistors, caps, etc, I simply want to buy an off the
shelf part which ONLY requires +5 volts, GND and a wire to connect it
to the reset line on my PCB. I don't want to have to wire up other
parts to it to get it to work.

Does such a modern part exist?

Do a search for "microcontroller supervisor". Microchip makes several
flavors, one of which will probably handle your needs.

TC1270 ? Includes a manual reset pin, which may be handy here.
Digikey says they are in stock, at about $1 each. Another option,
that is if Microchip development tools are already set up and ready,
is to use a PIC12F629, which includes a BOR and POR (and WDT), 128
bytes of EEPROM, has a comparator, timer, internal precision clock so
an external one isn't required, works from 2V-5.5V, is about 10-15
cents cheaper in ones, probably more readily available as it is in
wider use I think, and includes the ability to add other special
features. Of course, there is the programming problem. So back to
the $1 part for one-off simplicity.

Jon

 

[Jon Kirwan]

On Sat, 30 May 2009 19:08:29 -0700, Jon Kirwan
<jonk@infinitefactors.org> wrote:

is about 10-15 cents cheaper in ones

Sorry, it's 30 cents more expensive in ones! I had picked up some on
a special deal, which isn't available anymore. So that's old news.

Jon

 

[BobW]

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:r2q32519l9evio1j0hfltm2k9u83ura46b@4ax.com...

On Sat, 30 May 2009 19:08:29 -0700, Jon Kirwan
jonk@infinitefactors.org> wrote:

is about 10-15 cents cheaper in ones

Sorry, it's 30 cents more expensive in ones! I had picked up some on
a special deal, which isn't available anymore. So that's old news.

Jon

Please remember that we're still in a recession, Jon.

Bob
--
== All google group posts are automatically deleted due to spam ==

 

[Jon Kirwan]

On Sat, 30 May 2009 19:31:55 -0700, "BobW"
<nimby_GIMME_SOME_SPAM@roadrunner.com> wrote:

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:r2q32519l9evio1j0hfltm2k9u83ura46b@4ax.com...
On Sat, 30 May 2009 19:08:29 -0700, Jon Kirwan
jonk@infinitefactors.org> wrote:

is about 10-15 cents cheaper in ones

Sorry, it's 30 cents more expensive in ones! I had picked up some on
a special deal, which isn't available anymore. So that's old news.

Jon

Please remember that we're still in a recession, Jon.

Bob

And will be still, for some time.

Oh, well.

Jon

P.S.
What I'd like to see, micro-wise, is a 6-pin SOT23-6, programmable
level BOR, good quality POR, comparator, internal vref, 4 I/O
(guaranteed high impedance during reset), small EEPROM, 32kHz internal
low power (<1uA) and a 1MIP or better high speed available (internally
calibratable), operating voltage from 1.5V to 15V (upper limit of
CD4000 series), and at least one timer that can run while the cpu is
shut down (and wake it up on compare events.)

The closest I know about is the PIC12F683, at about a buck and a half
or maybe a little less on a good day, and 8 pins instead of 6. I
could buy a million, get a good price, and sell the other 999,999, I
suppose. But I'm too lazy.

I like the MSP430 hardware design (I can dither the clock, it's got
great B7 timer system, good peripherals all 'round), but I think the
smallest is 14-pin. And too big.

 

[Andy]

On Sat, 30 May 2009 22:25:19 GMT, jamma-plusser@hotmail.com
(jamma-plusser) wrote:

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some circuit
using TTLs and resistors, caps, etc, I simply want to buy an off the
shelf part which ONLY requires +5 volts, GND and a wire to connect it
to the reset line on my PCB. I don't want to have to wire up other
parts to it to get it to work.

Does such a modern part exist?

MAX6326, MAX6327, MAX6328, MAX6346, MAX6347, MAX6348
3-Pin, Ultra-Low-Power SC70/SOT ľP Reset Circuits

Industry's Lowest-Power Reset IC Consumes Only 500nA with No External
Components Required

Thanks

 

[Baron]

jamma-plusser wrote:

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some circuit
using TTLs and resistors, caps, etc, I simply want to buy an off the
shelf part which ONLY requires +5 volts, GND and a wire to connect it
to the reset line on my PCB. I don't want to have to wire up other
parts to it to get it to work.

Does such a modern part exist?

Thanks

Do it the old way with an RC to the reset pin !

--
Best Regards:
Baron.

 

[Michael Black]

On Sun, 31 May 2009, Baron wrote:

jamma-plusser wrote:

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some circuit
using TTLs and resistors, caps, etc, I simply want to buy an off the
shelf part which ONLY requires +5 volts, GND and a wire to connect it
to the reset line on my PCB. I don't want to have to wire up other
parts to it to get it to work.

Does such a modern part exist?

Thanks

Do it the old way with an RC to the reset pin !

I wondered about that. I'm too lazy to dig in the box to

find a Z80 book, so I wondered if there was something more
complicated about the reset. There was a special IC for
the 8086, but that included the clock, so who knows. I don't
even know where I put the Osborne book that introduces the
8bit CPUs, it should be right in front of me.

But yes, a lot of CPUs just required a temporary grounding
to reset. They even included a schmidt trigger so bounce
wasn't a problem. That then made it easy for the introduction
of reset on power on, just a resistor to the +5v line and a capacitor
to ground.

You'd even see that, computers would arrive that required one
to press the reset button when power was turned on, and people
would write about adding a resistor and capacitor to have it
reset on startup. I seem to recall doing that with one single
board computer, maybe my OSI Superboard, but I can't remember.

The only way this wouldn't work is if the reset pin doesn't have
a schmidt trigger, in which case an external one might be needed,
or if for some reason the Z80 needed some more complicate reset
system (which seems hard to believe).

Michael

 

[Baron]

Michael Black wrote:

On Sun, 31 May 2009, Baron wrote:

jamma-plusser wrote:

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some
circuit using TTLs and resistors, caps, etc, I simply want to buy an
off the shelf part which ONLY requires +5 volts, GND and a wire to
connect it to the reset line on my PCB. I don't want to have to wire
up other parts to it to get it to work.

Does such a modern part exist?

Thanks

Do it the old way with an RC to the reset pin !

I wondered about that. I'm too lazy to dig in the box to
find a Z80 book, so I wondered if there was something more
complicated about the reset. There was a special IC for
the 8086, but that included the clock, so who knows. I don't
even know where I put the Osborne book that introduces the
8bit CPUs, it should be right in front of me.

But yes, a lot of CPUs just required a temporary grounding
to reset. They even included a schmidt trigger so bounce
wasn't a problem. That then made it easy for the introduction
of reset on power on, just a resistor to the +5v line and a capacitor
to ground.

Every Z80 I ever had did it with an RC to the reset pin ! It has become
more complex since. As you rightly say the X86 also required T to be
reset as well.

You'd even see that, computers would arrive that required one
to press the reset button when power was turned on, and people
would write about adding a resistor and capacitor to have it
reset on startup. I seem to recall doing that with one single
board computer, maybe my OSI Superboard, but I can't remember.

I don't remember those but I do remember wiring a reset switch to most
of the earlier machines including the 8088/8086 and Amstrad 1512/1640
that never had one factory fitted.

I vaguely remember one of the early machines that used to blow up the
PSU if you switched it off and on again without waiting for 30 seconds
or so.

The only way this wouldn't work is if the reset pin doesn't have
a schmidt trigger, in which case an external one might be needed,
or if for some reason the Z80 needed some more complicate reset
system (which seems hard to believe).

Michael

Agreed !

--
Best Regards:
Baron.

 

[Don McKenzie]

jamma-plusser wrote:

I need to make up a reset circuit to reset, on power on, a Z80 (old
40-pin DIP type) and a few TTLs. I don't want to make up some circuit
using TTLs and resistors, caps, etc, I simply want to buy an off the
shelf part which ONLY requires +5 volts, GND and a wire to connect it
to the reset line on my PCB. I don't want to have to wire up other
parts to it to get it to work.

Does such a modern part exist?

Perhaps this is what you are seeking:
http://www.dontronics-shop.com/mc34064p-5.html

Don...


--
Don McKenzie

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