Is this 8-bit or 10-bit microcontroller

[devonsc]

10 bit adc on 8 bit microcontroller

Hi,

Hope you guys don't mind guiding a newbie like me. Thanks in advance...

I'm a little confuse in determining the category of a microcontroller, such as a 8-bit MCU or a 10-bit MCU. Say, for HC711E9, this is 8-bit, right?

But if we are talking about HC12BE32 (as attached is the location of the summary obtained from Freescale's website for this product)

https://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=68HC12BE32&nodeId=0162468636g3Jm#

Is it true that if the ports for the microcontroller is, say from 0-7, which is a total of 8, it means the specific microcontroller is categorized as 8-bit microcontroller?

If this is true, I'm confused as the ports for HC12BE32 are 0-7, which is a total of 8, does it mean that this is a 8-bit microcontroller? However, it is stated in the summary that it has 10-bit ADC. Sorry for such simple question, hope you guys don't mind guiding me. So, this HC12BE32 is actually a 8-bit MCU or 10-bit MCU?

Thanks a lot in advance.

 

[jdhar]

microcontroller with

The number of bits usually refers to either the internal data or address bus width - it has nothing to do with it's ports. It can have a 64-bit port for IO, but still be an 8-bit micro. Usually, 8 bit micro means that each instruction word can be characterized by 8-bits - and it usually refers to the addressing capabilities too. For eg, a 32-bit CPU can address 2^32, or 4Gb of memory.

 

[Buzzz]

writing 10-bit data to 8-bit memory

Hi there!

The number of pins on a port is not the part that determines whether a controller is 8, 10 or 16 bits (there are even more).
Ppl, correct me if I'm wrong, but I was taught that it depends on the controller's databus. So an 8 bit controller has an 8 bit wide databus. Your 68HC12BE32 is 16 bit, like your link says. So it has a 16 bits databus, but can indeed have 8 pins per port.

edit: JDHAR was not only quicker than I am, but also explains it more clear! :wink:

 

[devonsc]

32 bit alu output bits input bits

Hi jdhar and Buzzz,

Thanks for your concern. Pardon me, I don't quite understand this:

It can have a 64-bit port for IO, but still be an 8-bit micro.

Does it mean that, if a MCU have 8 ports with each ports having 8-bit data/address lines, it means 8x8=64 here? Sorry if this is nonsense.

For eg, a 32-bit CPU can address 2^32, or 4Gb of memory.

Usually, when we refer to memory, are we referring to the EEPROM or EPROM? Sorry for all my nonsense. Hope you guys don't mind guiding me in further understanding the basics of MCU. Thanks a lot in advance.

 

[kieennx]

Hi all,
I'm agree with Buzzz. An n-bit MCU is simple a MCU with n-bit data bus inside. This is basic knowledge of microprocessor technique.
There are 3 type of signal bus inside a MCU or MPU: data bus, address bus and control bus. 8051, PIC, AVR, 68HC11... have 8bit data bus, so they are called 8bit MCUs. 8086, 80C196 (and many more...) have 16-bit data bus, so they are called 16bit MPUs, MCUs. And so on...
There nothing related to number of ports or number of pins per port here! I/O ports are simple signals that allow CPU exchange data with outside world.
Hope this help.
Kieennx.

 

[echo47]

An 8-bit micro could have a 64-bit I/O port, although I've never seen such a chip. The port would be double-buffered, so the program can write eight separate bytes, and then all 64 output bits would change simultaneously. A 64-bit input port would work the other way around, simultaneously latching all 64 input bits, and then the program reads them one byte at a time.

A 32-bit CPU will have a 32-bit ALU. The address bus can be a different size.

 

[jdhar]

The point was not the size of the IO port, so I think you are getting into way too much detail that's not neccessary. The point is that the IO port size is different than the chip characterization size.

 

[tofinhk]

From my opinion, 10-bit ADC is not a consideration for ?-bit MCU. Same as what kieennx said, n-bit MCU contains n-bit data bus.
If you read carefully about the datasheet, you may find the format of the ADC return value on p.286 of Chapter 17, and you will know more about it. Even it is a 10-bit ADC, it returns 16-bit data.

 

[afti_khan]

just check the book "8051 uC" by Scott Mackenzie

 

[ace1903]

Microcontroller IO subsystem usually is not in direct connection with microprocessor ALU width . Example x86 architecture can access 8bit ports ,16bit bit ports and so on..