Problems understanding pin connections

Hello !

Can anyone direct me to a good guide which explains the differences between 
"common" microcontroller pin types, such as "open-drain" or "push-pull" etc 
?

The reason I'm asking this is that I'm trying to connect a TEA5768HL's 
SWPORT1 to a C8051F320's input port pin and I'm not sure how I should do it 
to make sure it works correctly. I've contacted Philips asking them the same 
question, but while they're able to help me with this specific issue, I 
would like to understand what it's all about so I don't have to ask again 
when I move on to another product or project.

Greetings,
Antti Keskinen 

Antti Keskinen wrote:

> Hello !
> 
> Can anyone direct me to a good guide which explains the differences between 
> "common" microcontroller pin types, such as "open-drain" or "push-pull" etc 
> ?
> 
> The reason I'm asking this is that I'm trying to connect a TEA5768HL's 
> SWPORT1 to a C8051F320's input port pin and I'm not sure how I should do it 
> to make sure it works correctly. I've contacted Philips asking them the same 
> question, but while they're able to help me with this specific issue, I 
> would like to understand what it's all about so I don't have to ask again 
> when I move on to another product or project.
> 
> Greetings,
> Antti Keskinen 
> 
> 
Any good book that explains digital logic should do this.  I would 
imagine it's in the ARRL handbook or "The Art of Electronics" by 
Horowitz & Hill (I'm not sure, though).

Here's a quick guide, though:

"Push-pull" (normal output) -- Actively supplies current from VCC to 
pull the voltage up, and pulls current to VEE to pull the voltage down. 
  In CMOS this means it has a P-type transistor to VCC and an N-type 
transistor to VEE.

"Open-drain" (or open collector) -- Has a transistor to ground, either 
N-type MOS or NPN in TTL.

"Tri-state" -- Has pull-up and pull-down transistors, with a control 
line to turn both off.  Hence, three states -- high voltage, low voltage 
or high impedance (to let other devices drive the line).

In addition to this you need to pay attention to old-style TTL logic 
interfaced to CMOS: a 5V TTL part is only guaranteed to drive about 2.7V 
or so as a "high", which is less than what 5V CMOS is guaranteed to 
respond to.  If you want to interface TTL to CMOS you have to use 
special CMOS parts with a lower threshold.  Ditto for interfacing parts 
with a 3.3V VSS to parts with a 5V VSS.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott wrote:
> 
... snip ...
> 
> "Push-pull" (normal output) -- Actively supplies current from VCC
> to pull the voltage up, and pulls current to VEE to pull the
> voltage down.  In CMOS this means it has a P-type transistor to
> VCC and an N-type transistor to VEE.

You are thinking of "totem-pole" output, which may be performed by
either complementary devices (p and n channel) or by configuration
(common collector and common emitter circuits hooked together). 
The choice depends on the available semiconductor process.

Push-pull means two unidirectional outputs driving two sections of
an output transformer, in such a way that only one driver is
operational at at time (class B or C) or partially overlapped
(class A).  This is a left-over from vacuum tube days, when all
devices were effectively n-channel fets.

Open-collector (or open drain) circuits are normally used to
perform "wired or", which is better termed "wired and" for the
usual positive logic.  

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CBFalconer wrote:
> Tim Wescott wrote:
> 
> ... snip ...
> 
>>"Push-pull" (normal output) -- Actively supplies current from VCC
>>to pull the voltage up, and pulls current to VEE to pull the
>>voltage down.  In CMOS this means it has a P-type transistor to
>>VCC and an N-type transistor to VEE.
> 
> 
> You are thinking of "totem-pole" output, which may be performed by
> either complementary devices (p and n channel) or by configuration
> (common collector and common emitter circuits hooked together). 
> The choice depends on the available semiconductor process.
> 
> Push-pull means two unidirectional outputs driving two sections of
> an output transformer, in such a way that only one driver is
> operational at at time (class B or C) or partially overlapped
> (class A).  This is a left-over from vacuum tube days, when all
> devices were effectively n-channel fets.
> 
> Open-collector (or open drain) circuits are normally used to
> perform "wired or", which is better termed "wired and" for the
> usual positive logic.  
> 
Hmm.  I always thought that "totem pole" only referred to the stack of 
transistors in a TTL.  Now I'm going to have to go look at actual usage, 
'cause push-pull isn't a bad way to describe what's happening in general.

Maybe if we all just started to use the term it'll be adopted, since 
there aren't that many transformer finals out there to make things 
ambiguous.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

"Tim Wescott" <tim@seemywebsite.com> wrote in message 
news:kvydnXn6L9P8s3XenZ2dnUVZ_sKdnZ2d@web-ster.com...
>> You are thinking of "totem-pole" output, which may be performed by
>> either complementary devices (p and n channel) or by configuration
>> (common collector and common emitter circuits hooked together). The 
>> choice depends on the available semiconductor process.
>>
>> Push-pull means two unidirectional outputs driving two sections of
>> an output transformer, in such a way that only one driver is
>> operational at at time (class B or C) or partially overlapped
>> (class A).  This is a left-over from vacuum tube days, when all
>> devices were effectively n-channel fets.
>>
> Hmm.  I always thought that "totem pole" only referred to the stack of 
> transistors in a TTL.  Now I'm going to have to go look at actual usage, 
> 'cause push-pull isn't a bad way to describe what's happening in general.

Curious. I had thought that totem-pole referred to an output using two 
identical NPN transistors, as in TTL; while push-pull was the correct term 
for a complementary pair, as in CMOS. A little bit of googling tends to 
support this e.g.
  http://www.dancon.com/techsup/faq_answer_encoder.htm
  http://www.play-hookey.com/digital/electronics/ttl_gates.html

I'm quite happy to be proved wrong, though ;).

Steve
http://www.fivetrees.com