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HI all, I am trying to design an assembler in C based on some instruction sets. I want to read a assembly language file containing instructions. IN the hex file there is hex data, integer data and negative integer data. I need to convert that data into 8 bit hexadecimal data , out of which 6 bit represents hexadecimal data and the remaining 2 bit will be of opcode. For example ; ldc 0x1000 output: 00100000 (opcode of ldc is 00) ldc -3; output : fffffd00 (6 bit 2s complement of +3).

I am trying ltoa to convert the integer into hexadecimal, but its giving string as output so i am not able to append 0s . PLease suggest urgentl

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  • Why can you not append 0s to a string? Also, I suggest looking at the sscanf() and sprintf() functions (or variants) instead, they are probably going to be your best friends in a project like this Commented Dec 24, 2010 at 12:32

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You seem to confuse bits with nibbles. One hexadecimal digit represents 4 bits. The opcode can store a 24 bit constant, 6 nibbles. Read the value from the string with strtol() and left-shift it by 8. Or with the opcode.

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Thanks but i need to read data and convert into 8 bit hexadecimal data out of which 6 bit will represent the actual data and two LSBs will represent opcode.
You need to think about how you are going to store 0x1000 (4096) into 6 bits (2^6 = 64). At least 13 bits are required. No machine exists that has 2 bits for an opcode, that allows for only 4 instructions. I can only assume you are confusing bits and bytes. One byte requires two hexadecimal digits. en.wikipedia.org/wiki/Nibble

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