Good review - a bit of a feeling of deja vous all over again, but such is the nature in comparing types and families of architectures. The presentation also jogged a couple issues for review in an upcoming design which is completely worth the time to review this presentation!
Well, Thank you all for attending today's Continuing Education Series course on Selecting a 16-bit Microcontroller. Be sure to come back tomorrow for a final wrapup of this week's events and some final conclusions for Microcontrollers and System Considerations. Thanks Again and see you all tomorrow!
I did a Z80 ap 20 years ago that used the "second register set" and the NMI to do a software UART - the NMI pin was tied to a spare timer output. It used about 25% of the processor and saved adding an interface chip.
@mark.browne: We have to do the same thing now in TI launchpad series. We use the timer and an outmod register to output an appropriate set reset value wrt to the bit value.
Assy - so do I. I had to convert a system out of C as it outgrew it's ROM. It taught me a lot about how C does things and stepped up my assembly languge game to the next level. C is really very pretty assembly languge.
A more intricate form of stack transfer is to use the stack as a volitle place to put local data for a subroutine. Adressing of this data is then relative tothe stack pointer. THis can be done local to a subroutine and/or a way to pass data to a subroutine.
If you do this, make sure you understand your software and you do not end up popping someone else's data off the stack. You don't want a stack imbalance.
Bill, what you think about performance ratio between MSP430 and AVR?
Both are register-based architectures. The AVR is 8-bit and the MSP430 is 16-bit. The AVR seems to be more forgiving when it comes to power supply. Both have been around for a very long time.
Thanks for the presentations this week. I now understand many things that I was not even aware of. I especially appreciate that you answer the questions on line so that those that do not have Linkedin can benefit...
I did a Z80 ap 20 years ago that used the "second register set" and the NMI to do a software UART - the NMI pin was tied to a spare timer output. It used about 25% of the processor and saved adding an interface chip.
Now that is interesting. Always glad to hear a Z80 story.
I did a Z80 ap 20 years ago that used the "second register set" and the NMI to do a software UART - the NMI pin was tied to a spare timer output. It used about 25% of the processor and saved adding an interface chip.
There it goes. I am thinking of adding the PIC24 to my project now to offload Ethernet and USB from the PIC32 due to the length of time required to communicate with the ADCs, DACs, and counter.
Also you can continue to receive interrupts inside an interrupt handler. You can enable or disable this atleast in the msp430.
Yes, that is when we have nested interrupts. While in an ISR, another interrupt will be acknowledges ONLY if it is a higher priority interrupt than the currect interrupt routine.
Then there is no way that the mcu is 'deaf' when doing this. An interrupt at that point would simply do the interrupt house keeping and jump to the handler.
But during the interrupt stack push/pop hardware processing, other interrupts are ignored until AFTER the stack operation is finished.
There it goes. I am thinking of adding the PIC24 to my project now to offload Ethernet and USB from the PIC32 due to the length of time required to communicate with the ADCs, DACs, and counter.
@mark.browne : Then there is no way that the mcu is 'deaf' when doing this. An interrupt at that point would simply do the interrupt house keeping and jump to the handler.
I was working with the MC6832 for the DDIN units some time ago when I discovered that 32-bit was more challenging. So I went back to 16-bit and have been there ever since.
A more intricate form of stack transfer is to use the stack as a volitle place to put local data for a subroutine. Adressing of this data is then relative tothe stack pointer. THis can be done local to a subroutine and/or a way to pass data to a subroutine.
@Bill: I was working with the MC6832 for the DDIN units some time ago when I discovered that 32-bit was more challenging. So I went back to 16-bit and have been there ever since.
Bill, instead of a one time critical interrupt, how about a "smart interrupt" that requires some sort of handshaking to verify the interrupt was received and processed?
That sounds more like a UART function, which has Tx/Rx handshaking.
Bill, instead of a one time critical interrupt, how about a "smart interrupt" that requires some sort of handshaking to verify the interrupt was received and processed?
It sounds like the MCU is essentially deaf to the outside world during stack transfers. Is there any way to capture critical interrupts that may fall into that window?
No, which is why that interrupt overhead during stack transfers is such an important selection criteria.You've got to read the datasheet to get the actual figures. The Renesas RL78 I believe is pretty fast in the interrupt latency department.
Bill, I'm in the process of choosing a Micro for a project that needs 512MB of FLASH for Hughe tables. So I'm using an external SPI Flash. I need minimum 4KRAM to be able to write to the flash. But the application does not require much processing (no math, only two comunication links)... I had already chosen the Frescale ARM cortex M0.. But Now I'm wandering if I have made the right decision... Any comments?
You mught want to look at some of the larger 16-bit Flash micros. The Infineon C166/XC166 16-bit family has some devices with more than 512KBytes Flash, and special instructions for lookup tables. You may be able to do the whole thing on one chip, no SPI memory.
One issue not covered here is that for the developer, going from an 8 bit architecture to 32 bit involves a huge learning curve. The 32 bit micros have a staggering amount of registers and peripherals compared to an 8 bitter!
True, there is a steeper learning curve in using a 32-bit. Also, many 32-bit MCUs have protected memory modes. If you are not familiar with these modes, your code can suddenly stop working and you won't know why unless you RTFM.
It sounds like the MCU is essentially deaf to the outside world during stack transfers. Is there any way to capture critical interrupts that may fall into that window?
Bill, I'm in the process of choosing a Micro for a project that needs 512MB of FLASH for Hughe tables. So I'm using an external SPI Flash. I need minimum 4KRAM to be able to write to the flash. But the application does not require much processing (no math, only two comunication links)... I had already chosen the Frescale ARM cortex M0.. But Now I'm wandering if I have made the right decision... Any comments?
One issue not covered here is that for the developer, going from an 8 bit architecture to 32 bit involves a huge learning curve. The 32 bit micros have a staggering amount of registers and peripherals compared to an 8 bitter!
Is it efficient to use external RAM or external clock with 16-bits?
You can use an external clock. But using external RAM on a microcontrolelr system will slow down your system, and you will also waste I/O pins for the external buses.
what are the differences between register based and acumulated based microcontrollers? whats the impact on overall performance?
Well, register-based are going to be higher performance than accumulator-based becasue you can do more work in less insrtuctions. That also means more compact code.
Reg-ster-based means you have eight or more REGISTERS in teh core, any of which can be used as destination registers for arithmetic operations. This is, of course, assembly language, which is important to understand if you want to understand the microcontroller, even if you are programming in C.
Accumulator based is when the microcontroller's core architecture has only one core register, called an ACCUMULATOR, that is the ONLY destination register for any arithmetic operation.
Previously got by with 12 bit ADCs in measuring sensor data. System requirements now require 16 bit performance. Find we're having to go to external ADCs to meet performance requirements.
@Alaskaman66: the next course is always on the page after your login just below this weeks courses. The next group will show up in two weeks when the next class starts.
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