Z80 reset circuit

J

jamma-plusser

Guest
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
 
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

555 timer chip in a one shot config ?
Click to expand...
 
On May 31, 6:25 am, jamma-plus...@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?

Thanks
Click to expand...
I have came across this chip TL7705 a few times and I think this might
be what you've been looking. It has active high and active low reset
outputs and just required 2 cap and a 10K resistor.

The datasheet is here:

http://www.st.com/stonline/products/literature/ds/1528/tl7705.pdf

Allen
 
also try Maxim:

www.maxim-ic.com

MAX706 is an old part, still in DIP and they give free samples on 24 hour
delivery

--
Bill Naylor
www.electronworks.co.uk
Electronic Kits for Education and Fun


"jamma-plusser" <jamma-plusser@hotmail.com> wrote in message
news:4a21b262.131763640@news.zen.co.uk...
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
Click to expand...
 
Allen Bong wrote:
On May 31, 6:25 am, jamma-plus...@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?

Thanks

I have came across this chip TL7705 a few times and I think this might
be what you've been looking. It has active high and active low reset
outputs and just required 2 cap and a 10K resistor.

The datasheet is here:

http://www.st.com/stonline/products/literature/ds/1528/tl7705.pdf

Allen
Tsssk... A reset only needs a cap and a resistor, what do you need
Click to expand...
chips for??
 
On Mon, 01 Jun 2009 05:16:09 +0200, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnll> wrote:

Allen Bong wrote:
On May 31, 6:25 am, jamma-plus...@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?

Thanks

I have came across this chip TL7705 a few times and I think this might
be what you've been looking. It has active high and active low reset
outputs and just required 2 cap and a 10K resistor.

The datasheet is here:

http://www.st.com/stonline/products/literature/ds/1528/tl7705.pdf

Allen
Tsssk... A reset only needs a cap and a resistor, what do you need
chips for??
Click to expand...
To make the circuit actually reset?
 
krw wrote:
On Mon, 01 Jun 2009 05:16:09 +0200, Sjouke Burry
burrynulnulfour@ppllaanneett.nnll> wrote:

Allen Bong wrote:
On May 31, 6:25 am, jamma-plus...@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?

Thanks

I have came across this chip TL7705 a few times and I think this might
be what you've been looking. It has active high and active low reset
outputs and just required 2 cap and a 10K resistor.

The datasheet is here:

http://www.st.com/stonline/products/literature/ds/1528/tl7705.pdf

Allen
Tsssk... A reset only needs a cap and a resistor, what do you need
chips for??

To make the circuit actually reset?
Click to expand...

It is a real pain in the ass to use that RC circuit, when you have
multiple chips that need reset. I have had to add a reset generator to
equipment that had been used a few years in the field. The RC reset has
a ramp. That means that different chips reset at slightly different
points. I had some $5,000 edit suite interface systems for 1" Sony
broadcast video tape equipment that had become unstable. I looked at
the schematic, and saw a RC reset circuit. The sad thing was that the
PC board was designed for a 555 reset circuit they had deleted.


--
You can't have a sense of humor, if you have no sense!
 
On Mon, 01 Jun 2009 05:16:09 +0200, Sjouke Burry wrote:
Allen Bong wrote:
On May 31, 6:25 am, jamma-plus...@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?

I have came across this chip TL7705 a few times and I think this might
be what you've been looking. It has active high and active low reset
outputs and just required 2 cap and a 10K resistor.

The datasheet is here:

http://www.st.com/stonline/products/literature/ds/1528/tl7705.pdf

Tsssk... A reset only needs a cap and a resistor, what do you need
chips for??
Click to expand...
It's a Z-80, which is really persnickety when it comes to rise/fall
times of its inputs. I remember the heroics we used to have to do just
to clock the damn thing!

Cheers!
Rich
 
"Rich Grise" <richgrise@example.net> wrote in message
news:pan.2009.06.01.18.30.37.857492@example.net...
snip
It's a Z-80, which is really persnickety when it comes to rise/fall
times of its inputs. I remember the heroics we used to have to do just
to clock the damn thing!

Cheers!
Rich
Click to expand...
Come on Rich, we clocked the baby with a debounced push button!
There was nothing to it at all.
 
On Mon, 01 Jun 2009 10:48:06 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

krw wrote:

On Mon, 01 Jun 2009 05:16:09 +0200, Sjouke Burry
burrynulnulfour@ppllaanneett.nnll> wrote:

Allen Bong wrote:
On May 31, 6:25 am, jamma-plus...@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?

Thanks

I have came across this chip TL7705 a few times and I think this might
be what you've been looking. It has active high and active low reset
outputs and just required 2 cap and a 10K resistor.

The datasheet is here:

http://www.st.com/stonline/products/literature/ds/1528/tl7705.pdf

Allen
Tsssk... A reset only needs a cap and a resistor, what do you need
chips for??

To make the circuit actually reset?


It is a real pain in the ass to use that RC circuit, when you have
multiple chips that need reset. I have had to add a reset generator to
equipment that had been used a few years in the field. The RC reset has
a ramp. That means that different chips reset at slightly different
points. I had some $5,000 edit suite interface systems for 1" Sony
broadcast video tape equipment that had become unstable. I looked at
the schematic, and saw a RC reset circuit. The sad thing was that the
PC board was designed for a 555 reset circuit they had deleted.
Click to expand...
Simple R-C reset circuits are notoriously unreliable. A good reset
should be held *AT* reset during all conditions where the circuit may
be active (but perhaps not functional) until power is stable. A
simple R-C circuit cannot do this.
 
krw wrote:
Michael A. Terrell wrote:

It is a real pain in the ass to use that RC circuit, when you have
multiple chips that need reset. I have had to add a reset generator to
equipment that had been used a few years in the field. The RC reset has
a ramp. That means that different chips reset at slightly different
points. I had some $5,000 edit suite interface systems for 1" Sony
broadcast video tape equipment that had become unstable. I looked at
the schematic, and saw a RC reset circuit. The sad thing was that the
PC board was designed for a 555 reset circuit they had deleted.

Simple R-C reset circuits are notoriously unreliable. A good reset
should be held *AT* reset during all conditions where the circuit may
be active (but perhaps not functional) until power is stable. A
simple R-C circuit cannot do this.
Click to expand...

I agree 100%. The microprocessors and peripheral chips don't have
Schmitt triggers to shape the external reset, so it needs to be a well
formed reset that hold the system in reset at least a few clock cycles
more than the specifications, to allow for aging of the components. I
prefer to hold it in reset three to five times the specified clock
cycles, just to be sure.


--
You can't have a sense of humor, if you have no sense!
 
On Tue, 02 Jun 2009 00:40:19 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

krw wrote:

Michael A. Terrell wrote:

It is a real pain in the ass to use that RC circuit, when you have
multiple chips that need reset. I have had to add a reset generator to
equipment that had been used a few years in the field. The RC reset has
a ramp. That means that different chips reset at slightly different
points. I had some $5,000 edit suite interface systems for 1" Sony
broadcast video tape equipment that had become unstable. I looked at
the schematic, and saw a RC reset circuit. The sad thing was that the
PC board was designed for a 555 reset circuit they had deleted.

Simple R-C reset circuits are notoriously unreliable. A good reset
should be held *AT* reset during all conditions where the circuit may
be active (but perhaps not functional) until power is stable. A
simple R-C circuit cannot do this.


I agree 100%. The microprocessors and peripheral chips don't have
Schmitt triggers to shape the external reset, so it needs to be a well
formed reset that hold the system in reset at least a few clock cycles
more than the specifications, to allow for aging of the components. I
prefer to hold it in reset three to five times the specified clock
cycles, just to be sure.
Click to expand...
If you have an oscillator that has to start (and stabilize), you'd
better wait for it too. ;-)
 
krw wrote:
On Tue, 02 Jun 2009 00:40:19 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

Michael A. Terrell wrote:

It is a real pain in the ass to use that RC circuit, when you have
multiple chips that need reset. I have had to add a reset generator to
equipment that had been used a few years in the field. The RC reset has
a ramp. That means that different chips reset at slightly different
points. I had some $5,000 edit suite interface systems for 1" Sony
broadcast video tape equipment that had become unstable. I looked at
the schematic, and saw a RC reset circuit. The sad thing was that the
PC board was designed for a 555 reset circuit they had deleted.

Simple R-C reset circuits are notoriously unreliable. A good reset
should be held *AT* reset during all conditions where the circuit may
be active (but perhaps not functional) until power is stable. A
simple R-C circuit cannot do this.


I agree 100%. The microprocessors and peripheral chips don't have
Schmitt triggers to shape the external reset, so it needs to be a well
formed reset that hold the system in reset at least a few clock cycles
more than the specifications, to allow for aging of the components. I
prefer to hold it in reset three to five times the specified clock
cycles, just to be sure.

If you have an oscillator that has to start (and stabilize), you'd
better wait for it too. ;-)
Click to expand...

These used an external chroma source, and the CPU clock was divided
down from that. There was an internal fail safe source, but the unit
was useless without external sync & clock signals.


--
You can't have a sense of humor, if you have no sense!
 
On Wed, 03 Jun 2009 00:39:45 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

krw wrote:

On Tue, 02 Jun 2009 00:40:19 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

Michael A. Terrell wrote:

It is a real pain in the ass to use that RC circuit, when you have
multiple chips that need reset. I have had to add a reset generator to
equipment that had been used a few years in the field. The RC reset has
a ramp. That means that different chips reset at slightly different
points. I had some $5,000 edit suite interface systems for 1" Sony
broadcast video tape equipment that had become unstable. I looked at
the schematic, and saw a RC reset circuit. The sad thing was that the
PC board was designed for a 555 reset circuit they had deleted.

Simple R-C reset circuits are notoriously unreliable. A good reset
should be held *AT* reset during all conditions where the circuit may
be active (but perhaps not functional) until power is stable. A
simple R-C circuit cannot do this.


I agree 100%. The microprocessors and peripheral chips don't have
Schmitt triggers to shape the external reset, so it needs to be a well
formed reset that hold the system in reset at least a few clock cycles
more than the specifications, to allow for aging of the components. I
prefer to hold it in reset three to five times the specified clock
cycles, just to be sure.

If you have an oscillator that has to start (and stabilize), you'd
better wait for it too. ;-)


These used an external chroma source, and the CPU clock was divided
down from that. There was an internal fail safe source, but the unit
was useless without external sync & clock signals.
Click to expand...
I was speaking in the general sense. R-C resets suck because they
cannot be guaranteed to work.
 
In article <4a21b262.131763640@news.zen.co.uk>, jamma-
plusser@hotmail.com says...
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


Microchip and Dallas both make TO-92 packaged 3 terminal reset circuits.
Click to expand...
Like the DS1233.
They work well, allow the use of a push button in parallel with the
reset for manual resetting and you can specify the voltage range you
want it to reset at.

Jim
 
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