4 ms·

Besides the other comments, you can get 8051s at much lower power than M0s... think 1 picojoule per (8 bit) op vs 10 picojoules per (32 bit) op, give or take. I

by addaon 3y ago

Besides the other comments, you can get 8051s at much lower power than M0s... think 1 picojoule per (8 bit) op vs 10 picojoules per (32 bit) op, give or take. It's pretty common to see 8051s in the low power zone of microcontrollers that also have one or more 32 bit cores on them. Generally the low power zone (including the 8051) can be run off an external clock (so 25 MHz - 100 MHz) in the 1 mW range, or can be run off an RC oscillator at a lower speed (like 7 ± 3 MHz) in the 100 µA range, both of which usefully extend the ability of the system to monitor for wake events and decide when to bring those Arm big boys on line. Some can even take the 8051 down to your 32 kHz real time clock for < 40 µA operation.

RetroTechie 3y ago
> Some can even take the 8051 down to your 32 kHz real time clock for < 40 µA operation. Isn't that a somewhat common ability for µC's? Allowing for very low power standby, RTC functionality & doing useful work at a higher speed?
- addaon 3y ago
  Somewhat... I more often see the ability to run some fixed-function blocks (RTC, as you mentioned; also ADC running scheduled conversions with a digital comparator on conversion calling interrupt, as an example) running at this low a clock, with the model being that these low-speed peripherals wake up something else. Having the ability to run a useful set of peripherals /and/ do arbitrary very slow computations to decide about changing clock isn't universal. As an example, even if you had that capability, if you wanted to wake on a complicated condition of an ADC read, you might end up lower total energy use to wake up on the ADC conversion to the RC filter low-MHz speed, do the your computation, and either go back to sleep or continue to wake further, rather than do the computation itself at 32 kHz -- and certainly the former could be lower latency, depending on the complexity of computation.

by addaon 3y ago

RetroTechie 3y ago

> Some can even take the 8051 down to your 32 kHz real time clock for < 40 µA operation. Isn't that a somewhat common ability for µC's? Allowing for very low power standby, RTC functionality & doing useful work at a higher speed?

addaon 3y ago
Somewhat... I more often see the ability to run some fixed-function blocks (RTC, as you mentioned; also ADC running scheduled conversions with a digital comparator on conversion calling interrupt, as an example) running at this low a clock, with the model being that these low-speed peripherals wake up something else. Having the ability to run a useful set of peripherals /and/ do arbitrary very slow computations to decide about changing clock isn't universal. As an example, even if you had that capability, if you wanted to wake on a complicated condition of an ADC read, you might end up lower total energy use to wake up on the ADC conversion to the RC filter low-MHz speed, do the your computation, and either go back to sleep or continue to wake further, rather than do the computation itself at 32 kHz -- and certainly the former could be lower latency, depending on the complexity of computation.