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shifting bits in multiple bytes array

Krasimir Pashov

Hello All,

I have non-standart function that shifting bits in multi bytes.


Syntax:
 shift_left (address, bytes, value);

Parameters:
 address is a pointer to memory.

 bytes is a count of the number of bytes to work with

 value is a 0 to 1 to be shifted in.

Returns:
 0 or 1 for the bit shifted out

Function:
 Shifts a bit into an array or structure. The address may be an array identifier or an address to a structure (such as &data). Bit 0 of the lowest byte in RAM is treated as the LSB

Any idea how to implement efficient "C" code for 8051?

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    Let's just have that "Function" description so that we can read it without having to scroll off miles to the right:

    Function:
 Shifts a bit into an array or structure.
 The address may be an array identifier or an address to a structure (such as &data).
 Bit 0 of the lowest byte in RAM is treated as the LSB

    "Any idea how to implement efficient 'C' code for 8051?"

    So what have you tried?
    Where are you stuck?

    I would suggest that the way to approach is to start with a general approach - don't worry about "efficiency" (whatever that means here) or 8051 specifics.

    Draw out on paper what needs to happen.

    Implement that using standard 'C' features, operators, etc.

    Test on a PC.

    Only when you have something that works in general, move on to think about what specific features the 8051 hardware and Keil C51 tools have that could optimise this.

Reply
  • 0

    Let's just have that "Function" description so that we can read it without having to scroll off miles to the right:

    Function:
 Shifts a bit into an array or structure.
 The address may be an array identifier or an address to a structure (such as &data).
 Bit 0 of the lowest byte in RAM is treated as the LSB

    "Any idea how to implement efficient 'C' code for 8051?"

    So what have you tried?
    Where are you stuck?

    I would suggest that the way to approach is to start with a general approach - don't worry about "efficiency" (whatever that means here) or 8051 specifics.

    Draw out on paper what needs to happen.

    Implement that using standard 'C' features, operators, etc.

    Test on a PC.

    Only when you have something that works in general, move on to think about what specific features the 8051 hardware and Keil C51 tools have that could optimise this.

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