Plain TTL, or even LS TTL is as old and outdated as 4000 CMOS and they chew
current as well. There are a multitude of devices you can use in the 74
format though. Even the 74HC series will be better from current sink point
of view. 

It all depends what you want to accomplish as part of the bigger picture.
If this is part of self education and you need easy access to parts, by
all means use 74HC parts. 

If you want more esoteric latching parts with higher drive capabilty, try
looking at some parts by Allegro
http://www.allegromicro.com/ic/

Texas Instuments and ON Semi used to make compatible stuff, I am not sure
if they still do. Try also ST and Philips as well. They sometimes have
some very interesting devices for esoteric applications.

-Aubrey

>antedeluvian wrote:
>> MM
>>
>> Take a look at this URL fro 28pin PICs. Scroll down looking for UARTS.
(Of
>> course you could bit bang a serial port)
>
>Bit banging is what others have done with the 16F84, but given that
>there are alternatives with inbuilt USART it seems churlish not to use
>one!
>
>>http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1092&mid=10&lang=en&pageId=74
>
>Thanks for that. Crikey! Microchip certainly do have a plethora of
>MCUs!
>
>> As far as current is concerned, you should really consult a data sheet.
A
>> lot depends on the range of temperature you are going to operate in
and
>> what voltage you can let the output rise to (in the case of current
sink).
>> The outout voltage will increase as the current increases. If you are
using
>> the output to drive other logic, this can prove a problem.
>
>No, the 4099 would drive just LEDs, up to eight, one per output.
>
>> Using the TI data sheet, assuming that you are only operating at 25
degC,
>> and that you are sinking current through the LED, you will need a
resistor
>> of ((5-0.4)/0.51)Kohms in series with the LED. The device can sink
0.51mA
>> guaranteed in the above circumstance with a 5V supply. I doubt you
will
>> even see a dull glow from a "bog standard" LED. You may want to try
low
>> current devices like the HLMP1700 which can work down to 0.5mA within
>> limits.
>
>How about if a TTL chip were used instead of a CMOS? Mind you, I'm sure
>I've hooked up an LED to a CMOS output in the past (with resistor) and
>there's not been a problem.
>
>MM
>
>

antedeluvian wrote:
> MM
>
> Take a look at this URL fro 28pin PICs. Scroll down looking for UARTS. (Of
> course you could bit bang a serial port)

Bit banging is what others have done with the 16F84, but given that
there are alternatives with inbuilt USART it seems churlish not to use
one!

>http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1092&mid=10&lang=en&pageId=74

Thanks for that. Crikey! Microchip certainly do have a plethora of
MCUs!

> As far as current is concerned, you should really consult a data sheet. A
> lot depends on the range of temperature you are going to operate in and
> what voltage you can let the output rise to (in the case of current sink).
> The outout voltage will increase as the current increases. If you are using
> the output to drive other logic, this can prove a problem.

No, the 4099 would drive just LEDs, up to eight, one per output.

> Using the TI data sheet, assuming that you are only operating at 25 degC,
> and that you are sinking current through the LED, you will need a resistor
> of ((5-0.4)/0.51)Kohms in series with the LED. The device can sink 0.51mA
> guaranteed in the above circumstance with a 5V supply. I doubt you will
> even see a dull glow from a "bog standard" LED. You may want to try low
> current devices like the HLMP1700 which can work down to 0.5mA within
> limits.

How about if a TTL chip were used instead of a CMOS? Mind you, I'm sure
I've hooked up an LED to a CMOS output in the past (with resistor) and
there's not been a problem.

MM

MM

Take a look at this URL fro 28pin PICs. Scroll down looking for UARTS. (Of
course you could bit bang a serial port)
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1092&mid=10&lang=en&pageId=74

As far as current is concerned, you should really consult a data sheet. A
lot depends on the range of temperature you are going to operate in and
what voltage you can let the output rise to (in the case of current sink).
The outout voltage will increase as the current increases. If you are using
the output to drive other logic, this can prove a problem.

Using the TI data sheet, assuming that you are only operating at 25 degC,
and that you are sinking current through the LED, you will need a resistor
of ((5-0.4)/0.51)Kohms in series with the LED. The device can sink 0.51mA
guaranteed in the above circumstance with a 5V supply. I doubt you will
even see a dull glow from a "bog standard" LED. You may want to try low
current devices like the HLMP1700 which can work down to 0.5mA within
limits.

You seemed to imply earlier that this was an existing circuit; if it is
you are going to have to be a lot more specific to provide help. If not,
it would be simple to add some form of driver to increase the current. 

>antedeluvian wrote:
>> MM
>>
>> For the PIC, do you need an A/D or not?
>
>No.
>
>
>> AS far as the 4099s are concerned, they cannot drive much current.
Make
>> sure you use low current LEDs.
>
>What about the bog-standard ones I can get from Maplin? (Each 4099 may
>have to drive a maximum of 8 LEDs, one per output pin.)
>
>MM
>
>

As far I concern there is variation of 74HC that  could replace 4099
(try 74HC59X or 74HC57X in that range). I would try make use of 74HC
since 4099 belong to ice age now. They bound to phase out very soon,
just like window 3.1 and 95.

It can work on 3.3 V or 5V, better output drive, faster and more stable
device than 4099.

Riscy.

antedeluvian wrote:
> MM
>
> For the PIC, do you need an A/D or not?

No.

> AS far as the 4099s are concerned, they cannot drive much current. Make
> sure you use low current LEDs.

What about the bog-standard ones I can get from Maplin? (Each 4099 may
have to drive a maximum of 8 LEDs, one per output pin.)

MM

MM

For the PIC, do you need an A/D or not?

AS far as the 4099s are concerned, they cannot drive much current. Make
sure you use low current LEDs.

-Aubrey


>antedeluvian wrote:
>> MM,
>>
>> The way I understand your question is that you want to replace a
74HC259
>> with a 4099. If this is the case, then you should know that aside from
>> anything else, they are not pin compatible. Secondly the Clear
function
>> appears to be inverse between the devices.
>>
>> Digikey seems to have plenty 4099s, so you don't need a circuit
redesign.
>>
>> Generally you need to consider several things when replacing one
technolgy
>> with another. Firstly the setup times and write times are normally
much
>> longer in 4000 series CMOS. The 74HC series is quicker so you probably
>> could make the substitution (if pin equivalent), but you do need to
make
>> sure the timing is OK.
>>
>> Driving 4000 series from any TTL output normally requires a pull up
>> resistor to ensure logic high level compatibilty (provided they are
both
>> run from 5V) unless the 4000 series device has Schmitt trigger inputs
>> (which the 4099 does not). Drive levels of the 4000 series into TTL
can
>> prove problematic. You need to investigate the output drive capabilty
of
>> the CMOS part.
>>
>> The 4000 CMOS series can operate with a supply voltage from 3V to 15V.
>> This can be advantageous in some circumstances, but obviously
interfacing
>> with 5V systems would need extra attention.
>>
>> -Aubrey
>
>Thanks for that, Aubrey. Okay, I now have found Cricklewood Electronics
>that also do the 4099. Like I said, I'm a novice so when some of the
>main catalogues  didn't stock it I assumed it had become outdated and
>little sought after.
>
>By the way, the 4099s will be driving LEDs, one per pin. This is in
>conjunction with MIDI.
>
>Since I'm here, what's the next best choice to the 16F628(A)? I was
>intending to use it in preference to a 16F84 because the former comes
>with an inbuilt USART. However, that utilises RB1 and RB2 as RX/TX
>respectively, which thus lose me those pins as outputs. Pin 8 (RB2/TX)
>apparently cannot be configured as a bog-standard output when the USART
>is invoked, even if TX is not required. And all the other pins that
>could be outputs are already used up.
>
>Therefore I am now considering the 16F877 instead, which has many more
>pins to play with. However, this PIC is twice the price and has a lot
>of additional functionality/capacity that I don't need. Is there
>something in between? For example, do any of the 28-pin PICs have a
>USART?
>
>MM
>
>

antedeluvian wrote:
> MM,
>
> The way I understand your question is that you want to replace a 74HC259
> with a 4099. If this is the case, then you should know that aside from
> anything else, they are not pin compatible. Secondly the Clear function
> appears to be inverse between the devices.
>
> Digikey seems to have plenty 4099s, so you don't need a circuit redesign.
>
> Generally you need to consider several things when replacing one technolgy
> with another. Firstly the setup times and write times are normally much
> longer in 4000 series CMOS. The 74HC series is quicker so you probably
> could make the substitution (if pin equivalent), but you do need to make
> sure the timing is OK.
>
> Driving 4000 series from any TTL output normally requires a pull up
> resistor to ensure logic high level compatibilty (provided they are both
> run from 5V) unless the 4000 series device has Schmitt trigger inputs
> (which the 4099 does not). Drive levels of the 4000 series into TTL can
> prove problematic. You need to investigate the output drive capabilty of
> the CMOS part.
>
> The 4000 CMOS series can operate with a supply voltage from 3V to 15V.
> This can be advantageous in some circumstances, but obviously interfacing
> with 5V systems would need extra attention.
>
> -Aubrey

Thanks for that, Aubrey. Okay, I now have found Cricklewood Electronics
that also do the 4099. Like I said, I'm a novice so when some of the
main catalogues  didn't stock it I assumed it had become outdated and
little sought after.

By the way, the 4099s will be driving LEDs, one per pin. This is in
conjunction with MIDI.

Since I'm here, what's the next best choice to the 16F628(A)? I was
intending to use it in preference to a 16F84 because the former comes
with an inbuilt USART. However, that utilises RB1 and RB2 as RX/TX
respectively, which thus lose me those pins as outputs. Pin 8 (RB2/TX)
apparently cannot be configured as a bog-standard output when the USART
is invoked, even if TX is not required. And all the other pins that
could be outputs are already used up.

Therefore I am now considering the 16F877 instead, which has many more
pins to play with. However, this PIC is twice the price and has a lot
of additional functionality/capacity that I don't need. Is there
something in between? For example, do any of the 28-pin PICs have a
USART?

MM

MM,

The way I understand your question is that you want to replace a 74HC259
with a 4099. If this is the case, then you should know that aside from
anything else, they are not pin compatible. Secondly the Clear function
appears to be inverse between the devices. 

Digikey seems to have plenty 4099s, so you don't need a circuit redesign.

Generally you need to consider several things when replacing one technolgy
with another. Firstly the setup times and write times are normally much
longer in 4000 series CMOS. The 74HC series is quicker so you probably
could make the substitution (if pin equivalent), but you do need to make
sure the timing is OK.

Driving 4000 series from any TTL output normally requires a pull up
resistor to ensure logic high level compatibilty (provided they are both
run from 5V) unless the 4000 series device has Schmitt trigger inputs
(which the 4099 does not). Drive levels of the 4000 series into TTL can
prove problematic. You need to investigate the output drive capabilty of
the CMOS part.

The 4000 CMOS series can operate with a supply voltage from 3V to 15V.
This can be advantageous in some circumstances, but obviously interfacing
with 5V systems would need extra attention.

-Aubrey

>On Wed, 26 Oct 2005 16:28:36 GMT, Tauno Voipio
><tauno.voipio@INVALIDiki.fi> wrote:
>
>>MM wrote:
>>> Is anything to be gained from substituting 74HC/HCT259 chips for CMOS
>>> 4099 ones? The 4099 chips shown in the circuit in question hook up to
>>> a 16F84 PIC and to a 74LS138.
>>
>>What do you think to gain?
>
>Dunno! I am a novice. (Okay, I have picked up a soldering iron
>occasionally and built some circuits.) The reason I asked was because
>the 4099 doesn't seem widely available any more, so I thought that's
>because it's been superseded.
>
>MM
>

This message was sent using the comp.arch.embedded web interface on
www.EmbeddedRelated.com

On Wed, 26 Oct 2005 16:28:36 GMT, Tauno Voipio
<tauno.voipio@INVALIDiki.fi> wrote:

>MM wrote:
>> Is anything to be gained from substituting 74HC/HCT259 chips for CMOS
>> 4099 ones? The 4099 chips shown in the circuit in question hook up to
>> a 16F84 PIC and to a 74LS138.
>
>What do you think to gain?

Dunno! I am a novice. (Okay, I have picked up a soldering iron
occasionally and built some circuits.) The reason I asked was because
the 4099 doesn't seem widely available any more, so I thought that's
because it's been superseded.

MM