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difference between 8 bit & 16 bit controllers

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  • difference between 8 bit & 16 bit controllers

    when we are dealing with controllers they differ in bits which represents no of bits accessed at a time like in 8 bit controllers we can access 8 bits at a time but i have seen that even in MSP430 which is a 16 bit controller we access 8 bits at a time ...so how MSP430 is a 16 bit controller ....WHY??????

  • #2
    By 8 bits access - do you mean port values ?

    Otherwise 16-bit means the width of the registers. A 16-bit microprocessor / controller can process data and memory addresses that are represented by 16 bits.

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    • #3
      hi
      its the DATA and the ADD BUS size
      the MSP430 is 16 bit

      8 bit : 00000000 capable of doing number up to 255 (0-255)

      16 bit: 00000000_00000000 capable of doing numbers up to 65535 (0-65535)

      32 bit: 00000000_00000000_00000000_00000000 capable of doing numbers up to 4294967295 (0-4294967295)

      The bit level is how many bits the controller can handle

      http://www.coactionos.com/embedded-d...ntrollers.html

      http://www.differencebetween.net/tec...crocontroller/

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      • #4
        Originally posted by Knewron View Post
        By 8 bits access - do you mean port values ?

        Otherwise 16-bit means the width of the registers. A 16-bit microprocessor / controller can process data and memory addresses that are represented by 16 bits.
        by 8 bit access i mean 8 bits registers access like PORTx register

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        • #5
          Originally posted by Kunal Mehindru View Post
          by 8 bit access i mean 8 bits registers access like PORTx register


          hi
          Oh no that's not right

          Otherwise

          08 bit Register 08 Ports
          16 bit Register 16 Ports
          32 bit Register 32 Ports
          64 bit Register 64 Ports
          128 bit Register 128 Ports
          256 bit Register 256 Ports
          512 bit Register 512 Ports
          1024 bit Register 1024 Ports
          .................................................. ....etc .

          The LPC1110/11/12/13/14/15 are a ARM Cortex-M0 based, low-cost 32-bit MCU family,
          designed for 8/16-bit microcontroller applications, offering performance, low power, simple
          instruction set and memory addressing together with reduced code size compared to
          existing 8/16-bit architectures.
          The LPC1110/11/12/13/14/15 operate at CPU frequencies of up to 50 MHz.

          http://www.nxp.com/documents/data_sheet/LPC111X.pdf

          http://www.keil.com/dd/docs/datashts/st/st10f269_ds.pdf

          http://www.ti.com/lit/ds/symlink/msp430g2553.pdf

          http://www.ti.com/lit/ds/symlink/msp430g2211.pdf


          MSP 430G2553 & MSP 430G2211 both are 16 bit Micro controller's but have 24 and 10 GPIO respectively.


          How many Ports would you like to have on your Micro Controller ???????????
          Last edited by mkbutan; February 21st, 2013, 09:10 PM.

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          • #6
            i think they differ mainly in their databus

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            • #7
              Originally posted by niteshtripathi View Post
              i think they differ mainly in their databus

              hi
              yes you are partly Right
              Data Bus and Address Bus

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              • #8
                Bits of the microprocessors just simply indicates, how much large binary word it can process at a time. For example an 8 bit microprocessor can process 8 bit of binary word at a time. Alternatively, one can also understand it by comprehending an 8 bit microprocessor containing address bus of 8 lines.

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                • #9
                  hows address bus ????

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                  • #10
                    @Enfotsret-I think your name is also a spam..please dont do spam here in this forum..

                    Comment


                    • #11
                      MSP430 architecture

                      The question, difference between 8 bit and 16 bit microprocessors(microcontrollers) has a lot of bearing with the architectural difference of the microprocessor. The major architectural differences are given below
                      1. Length of the microprocessor's data word
                      2. The size of memory which the microprocessor can directly address
                      3. The speed at which the microprocessor can execute instructions

                      There are other architectural difference, one must know, to use the microprocessor with understanding (probably an assembly language programmer). These are
                      1. The number of registers avaialble to the programmer
                      2. The different types of registers avaialble to the programmer
                      3. The different type of instructions available to the programmer

                      The bit value (4, 8, 16, 32,64 etc) is the witdth of the data bus or data pipe size. Meaning that a 8 bit mcu can (for the most part) can only work with values from 0 to 255 for each clock cycle. Think of it as the processor has 8 digital lines in parallel. And a 16 bit has 16 lines, and 32 bit has 32 lines. So for each clock cycle, it reads these data lines, so the more lines the higher the value you can work with per clock cycle. Therefore, the following assumptions stand good.

                      8 bit = 2^8 = 256

                      16 bit = 2^16 = 65,536

                      32 bit = 2^32 = 4,294,967,296

                      The larger the data bus and address bus allows the processor to access larger memory addresses.

                      This makes a big difference during mathematical operations. A 16 bit number gives more precision than 8 bit numbers. 16 bit microcontrollers are also more efficient in processing math operations on numbers that are longer than 8 bits. A 16 bit microcontroller can automatically operate on two 16 bit numbers, like the common definition of an integer. But when you are using an 8 bit microcontroller, the process is not as straightforward. The functions implemented to operate on such numbers will take additional cycles. Depending on how processing intensive your application is and on how many calculations you do, this may affect the performance of the circuit.

                      The salient features of MSP430 design are listed below (courtsey - data sheet of msp430 series of micorcontrolers from Texas Instruments)

                      - RISC type architecture of the CPU is based on a short instruction set (27 instructions), interconnected by a 3-stage instruction pipeline for instruction decoding.
                      -The CPU has a 16-bit ALU, four dedicated registers and twelve working registers, which makes the MSP430 a high performance microcontroller suitable for low power applications.
                      -The addition of twelve working general purpose registers saves CPU cycles by allowing the storage of frequently used values and variables instead of using RAM.
                      -The orthogonal instruction set allows the use of any addressing The orthogonal instruction set allows the use of any addressing mode for any instruction, which makes programming clear and consistent, with few exceptions, increasing the compiler efficiency for high-level languages such as C.

                      -The MSP430 CPU includes an arithmetic logic unit (ALU) that handles addition, subtraction, comparison and logical (AND, OR, XOR) operations. ALU perations can affect the overflow, zero, negative, and carry flags in the status register.

                      -The CPU incorporates sixteen 16-bit registers: Four registers (R0, R1, R2 and R3) have dedicated functions; There are 12 working registers (R4 to R15) for general use.

                      Bottom Line : It is the prerogative of the circuit developer/application developer to identify the target mcu for the specific application. The more wider is the address and data bus the more will be the project cost. Therefore, please identify the requirement in terms of processing speed, type of operations to be performed etc before selecting the "width of the target mcu"

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                      • #12
                        Originally posted by Tapas Pattnaik View Post
                        @Enfotsret-I think your name is also a spam..please dont do spam here in this forum..
                        http://forum.electronicsforu.com/sho...ull=1#post5638

                        http://forum.electronicsforu.com/sho...ull=1#post5929

                        Hi
                        sir I had reported the same to Mr. di1in (Administrator) and its rectified now ENJOYYYYYYYYYYYYYYYYYY

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                        • #13
                          Hi
                          Thanks Mr. Vidya your information is very useful
                          keep it up

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                          • #14
                            Originally posted by Kunal Mehindru View Post
                            when we are dealing with controllers they differ in bits which represents no of bits accessed at a time like in 8 bit controllers we can access 8 bits at a time but i have seen that even in MSP430 which is a 16 bit controller we access 8 bits at a time ...so how MSP430 is a 16 bit controller ....WHY??????
                            16 bit controller provides the execution of 16 bit data in just one clock cycle. Whereas dealing with an 8 bit controller means we can process 8 bit data in one clock cycle but for processing 16 bit data, it will require 2 clock cycles.

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                            • #15
                              It should be data bus.

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