What is the clock speed Chip used for IPL from eeprom?

JohnR2010

I’m fleshing out the details of my next article. I plan on using a prop with no external crystal locked at the RCSLOW rate for everything. All the heavy lifting will be in PASM and so far, I have had plenty of horsepower at 20kHZ. There is not much going on just some IrD communications and driving a small stepper.
The primary reason for locking everything down to 20kHz is battery life and to reduce the possibility of generating EMI interference. However, it just occurred to me as I watched my test app load on the propeller that it may be running at RCFAST during IPL. I think I even read that is what Chip did to load the EEPROM as quick as he could. If this is the case, is there any way to lock IPL to RCSLOW 20Khz? I know the answer is no but I thought I would ask. Does anyone have a recommendation on another boot process that would allow me to stay at 20kHz?

jmg

JohnR2010 wrote: »

... If this is the case, is there any way to lock IPL to RCSLOW 20Khz? I know the answer is no but I thought I would ask. Does anyone have a recommendation on another boot process that would allow me to stay at 20kHz?

The datasheet has some Icc profiles
8.6. Current Profile at Various Startup Conditions
You cannot change the 50ms PUD and the 640us/1.25mA Pre-Boot load, and if you want to use only EEPROM, then that puts you into the 1.3~1.5s @ 2~2.2mA region.

Other ideas :
You might be able to lower Vcc during boot, to save energy ?
You could consider a small MCU to do UART boot instead, which gives you more control over the current/time profiles.
If your code is moderate, a 18kF MCU like N76E003 is quite low cost, and can save needing an EEPROM at all.

JohnR2010

jmg wrote: »

The datasheet has some Icc profiles
8.6. Current Profile at Various Startup Conditions
You cannot change the 50ms PUD and the 640us/1.25mA Pre-Boot load, and if you want to use only EEPROM, then that puts you into the 1.3~1.5s @ 2~2.2mA region.

Good stuff! I don’t think that much current is going to break me. The concern now is the clock speed he is using. I was hoping to ride this project through FCC part 15 testing as an exempted digital device. To qualify for that the highest frequency used must be less than 1.705 Mhz (there are several other requirements for exemption but for now clock speed is what I’m focused on).

I’m now struggling with how to calculate the fastest clock speed he uses during IPL??

Thanks for the input on the N76E003. I have seen others talk about replacing the EEPROM and I think even using it as a clock source. It adds more complexity than I want to deal with at this point.

jmg

JohnR2010 wrote: »

Good stuff! I don’t think that much current is going to break me. The concern now is the clock speed he is using. I was hoping to ride this project through FCC part 15 testing as an exempted digital device. To qualify for that the highest frequency used must be less than 1.705 Mhz (there are several other requirements for exemption but for now clock speed is what I’m focused on).

It's probably the external frequency that matters - that's all anyone can measure

That's easy enough to measure on the SCL pin.
With a 400kHz i2c spec common when P1 was designed, and margins, I think it is just over 300kHz and that is brief - so you are well under 1.705MHz
( average is indicated by 32768*9/1.3 = 226.855kHz)

JohnR2010

jmg wrote: »

That's easy enough to measure on the SCL pin.
With a 400kHz i2c spec common when P1 was designed, and margins, I think it is just over 300kHz and that is brief - so you are well under 1.705MHz
( average is indicated by 32768*9/1.3 = 226.855kHz)

Yea, yea, sure divide the size of the EEPROM by the 1.3 seconds it takes to load it! Thanks!! You just made my day!!

Cluso99

The Prop will always load 32KB from EEPROM. I have used 8KB EEPROMS but have to account for the prop to load 4 copies to make the 32KB hub.