Instruction Word Size in Intel 8085 microprocessor
Data types and literals. data types: instructions are all 32 bits ; byte(8 bits), halfword (2 bytes), word (4 bytes) a character requires 1 byte of storage cs107 handout 06 spring 2008 april the cpu executes the current instruction, some memory hardware systems keep a 9th parity bit for every byte so the hardware
... specify the operation of the instruction. the midrange instruction set summary in table 29-1 for byte-oriented instructions, 14-bit instruction word status instructions: assembly language reading: bit 0 or 1 byte 8 bits half word 16 bits this instruction (load byte)
Take, for example, an 8-bit system with 2 byte words. the instruction size is one word, but the bandwidth of the system is only 1/2 word. the system must be byte addressable so that it can load the instruction 1-byte at a time. it cannot be word addressable because it cannot handle a full word of data at a time. for any computer architecture with an eight-bit byte, the word will be some multiple of eight bits. in ibm's evolutionary system/360 architecture, a word is 32 bits, or four contiguous eight-bit bytes. in intel's pc processor architecture, a word is 16 bits, or two contiguous eight-bit bytes.
Multiple byte processing with full- word instructions the value of bit 0 of a mask byte is usually immaterial. we therefore define a the cbw (convert byte to word) instruction copies the sign (bit 7) (bit 15) of the word in the ax register into the higher 16 bits of the eax register.
Load/store byte instructions extended so as to support an eight bit twoвђ™s complement representation. the other bytes in the word are not affected. 4.2.1. ldr and str, words and unsigned bytes load register and store register, 32-bit word or 8-bit unsigned byte. byte loads are zero-extended to 32 bits. syntax
Double the size of the source operand by means of sign extension (see figure 7-6 in the ia-32 intel architecture software developer's manual, volume 1). the cbw (convert byte to word) instruction copies the sign (bit 7) in the source operand into every bit вђ¦ data types and literals. data types: instructions are all 32 bits ; byte(8 bits), halfword (2 bytes), word (4 bytes) a character requires 1 byte of storage
Real Machines with 16 32 and 30-bit words