PicBasic Pro 16F628A Clock speed help !

[andybarrett1]

Hi All

Using PBP 2.50C

Confused..... I am attempting to slow a 16F628A from the default 4Megs to 48K Clock Speed

Am I right in assuming the Command :-

PCON.3 = 0

At beginning of code should do it....

My code works fine at 4Megs and is not that complex... :-) Just drives a LCD and a few buttons.

Any help welcome

[ardhuru]

Hi Andy,

The 16F628A does not have a frequency multiplier; you can either use the internal osc at 4 Mhz, or an external crystal upto a maximum of 20 Mhz.

Regards,

Anand

Oops, sorry read the 48 Khz as MHz

[HenrikOlsson]

Hi,
Yes, as far as I can see setting PCON.3=0 should switch from 4Mhz (default) to 48kHz.
However, PBP doesn't have a suitable DEFINE OSC xx for that frequency so all software timed commands will be off by a factor of about 83 (if you're using the default DEFINE OSC 4), ie a PAUSE 10 will in reality be a PAUSE 830 and so on. This affects ALL selftimed commands, like PULSIN/OUT, SERIN/OUT, LCDOUT, PAUSE, PAUSEUS, PWM and so on.

For LCDOUT perhaps you could try changing your data and command delays by a factor of ~80 and see what happens. I'm not saying it'll work but it's worth a try. If you have any PAUSE or PAUSEUS in your code then you'd need to scale those too obviously.

/Henrik.

[Demon]

I'm curious why you would want to slow the PIC to 48 kHz. What requirement prevents you from running at 4 MHz?

It might be easier to run everything at 4 MHz and tweak whatever specific logic you want to simulate 48 kHz.

Robert

[ardhuru]

Battery conservation, perhaps?

[andybarrett1]

Yes…. Am attempting to use a pic in field from solar sources… so saving power is a premium !!!

[rsocor01]

Yes…. Am attempting to use a pic in field from solar sources… so saving power is a premium !!!

This is from the datasheet

• Standby Current:
- 100 nA @ 2.0V, typical
• Operating Current:
- 12μA @ 32 kHz, 2.0V, typical
- 120μA @ 1 MHz, 2.0V, typical

You can put the chip in standby mode and wake the chip up when needed using interrupts.

Robert

[andybarrett1]

This is from the datasheet



You can put the chip in standby mode and wake the chip up when needed using interrupts.

Robert

I Never thought of interrupts.... Even Better!!!

Thank you

[andybarrett1]

In Short ….

It should work,,,?

I understand Pause etc will be somewhat slower !

[andybarrett1]

Thank you all for help !

BR
Andy