I am looking for a 64-pin PIC processor with ST feature for

[MCUprogrammer]

Hello Everybody
I'm looking for a 64 pin 8 bit processor with all I/O pins ST capable. www.microchip.com I couldn't see an option with this feature. The features I'm looking for are;
- 8-bit processor
- working with 5 volts
- all I/Os are ST capable
I'm looking for a processor. Would you help me with this topic?
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Best Regards...
MCUprogrammer
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Work Hard

[temtronic]

Unlikely you'll find one, though maybe the Microchip search engine will ??
personally, I'd use the 74HCT540 as the buffer. Might add 6-7$ to the project, so less than 10 minutes of my actual R&D costs.

There may be other 'octal ST buffers', maybe cheaper, smaller, etc. the 540 is one I've used for decades.

[Ttelmah]

For 'reverse compatibility', just about all PIC's have at least one port that
supports TTL levels rather than ST. However a few of the newer chips
have the input level programmable on at least some of the pins using
the INLVL registers. So have a look at devices like the PIC16F19197. This
has such registers for all it's inputs, and is a 64pin device, so might
well suit.
I don't think the MicroChip search has any option for TTL/ST in the search,
so the way to work is to search for all the other parameters (8bit PIC and
64pin, plus any other peripheral requirements etc., that you have), and
then look in the data sheets for the pin logic levels.

[MCUprogrammer]

Thanks... so, I can see the Input Low Voltage and Input high Voltage values of the I/O PORTS PIC processor. How can I access the current values?
e.g
Input Low Current
Where writes current values such as Input high Current.
_________________
Best Regards...
MCUprogrammer
_______________________________
Work Hard

[temtronic]

Curious was I so... using the PIC18F46K22 datasheet...

Under 'electrical characteristics', parameter D155, Input leakage I/O...,0.1nA, max of 50nA.
PORTB weak pullups enabled = +-100 uA.

Essentially the current will be a function of VDD and the pullup resistor on a pin. There may be additional current drawn depending on the internal peripheral used for that pin though.

I think you'd need a real GOOD ammeter to measure nanoamps !

Why the interest in the current values ? If for a battery powered project, there are several other factors that are more important than the pin current.

[Ttelmah]

Key thing is that PIC inputs are CMOS. Now CMOS gates all have input
currents of almost zero. This is why you can do things like operate a CMOS
input with the voltage from a finger. What draws current is changing the level,
where you have to charge or discharge the capacitance in the pin. The
faster you want to change it, the more current is needed. This is also
why PIC pins are very sensitive to RF. The internal diode structures will
rectify an RF signal applied and you can get very significant voltages
on a pin. As Jay says, the actual DC current will really be determined by
what resistances are present (either external resistors or the internal
current sources).

[MCUprogrammer]

So actually these values should be in the datasheet? So I can pull the input of a PIC to 0 with how many ma. How can I find out the minimum and maximum value of this?
_________________
Best Regards...
MCUprogrammer
_______________________________
Work Hard

[temtronic]

Microchip uses a weak pulup to get 100uA, for portB spec...

I've used 10Mr as pullups to a VDD of 5 volts on 4000 series CMOS chips 3 decades ago....

learn by doing...
use a breadboard, insert various 'pullup resistors', have a PIC program read/display the I/O pin value, attach an oscilloscope to the pin as well to SEE the waveform

[Ttelmah]

The point is that there is almost no current needed at all to pull the pin either
high or low. What there is is an input capacitance, and the current you need
depends on how fast you want to change the voltage stored in this.
You could pull about 200PIC pins high with a 1mA signal. But given that
this many pins would have 1nF capacitance it'd take time to charge this
capacitor up.
Typical leakage is quoted at about 5nA, but the real figure is usually below
this.