Machine coding the programs-microprocessor, Assembly Language

Machine Coding the Programs

So far we have describe five programs which were  written  for hand coding  by a programmer. In this, we will now have a deep look at how these programs may be  translate to machine codes. In Appendix, the instruction set along with the Appendix is presented. This Appendix is self-explanatory to hand code mostly of the instructions. The V,S W, D, MOD, REG  and R/M  fields are appropriate decided depending upon the data types, addressing mode and the registers  used. The table shows the details about how to select these fields.

Most of the instructions either have particular opcodes or they may be decided only by setting the V,S, W, D, REG, MOD and R/M fields suitably but the critical point is  the calculation of jump addresses for intra segment branch instructions. Before beginning the coding of call or jump instructions, we will see some simpler coding examples.

Example :

MOV BL, CL

For hand coding this instruction, first we will have to note down the following features.

(i) It sets in the register/memory to/from register format.

(ii) It is an 8-bit operation.

(iii) BL is the destination register and CL is a source register.

Now from the feature (i) by using the Appendix, the op code format is given below.

1485_mcp.jpg

If d =1, then transformation of data is to the register shown by the REG field, for example the destination is a register (REG). If d = 0, the source is a register shown by the REG field. It is an 8-bit operation, therefore w bit is 0. If it had been a 16-bit operation, the w bit would have been 1.From referring to given table to search the REG to REG addressing in it, for example the last column with MOD 11. According to the Appendix when MOD is 11, the R/M field is treated as a REG field. The REG field which is used for source register and the R/M field are used for the destination register, if d is 0. If d =1, the REG field is utilized for destination and the R/M field is used to indicate source. the complete machine code of this instruction comes out to be now.

code    dw       MOD   REG    R/M

MOV BL, CL 1 0 0 0 1 0 0 0     1   1   001    0 1 1= 88 CB

Posted Date: 10/12/2012 6:47:59 AM | Location : United States







Related Discussions:- Machine coding the programs-microprocessor, Assignment Help, Ask Question on Machine coding the programs-microprocessor, Get Answer, Expert's Help, Machine coding the programs-microprocessor Discussions

Write discussion on Machine coding the programs-microprocessor
Your posts are moderated
Related Questions
programs

SHR : Shift Logical Right: This instruction performs bit-wise right shifts on the operand word or byte that might be reside in  a memory location or a register, by the specified c


code to add two matrices

LDS/LES Instruction execution :  LAHF : Load AH from Lower Byte of Flag: - This instruction loads the AH register with the lower byte of the flag register. This instruction ca

Write Policy A write policy determines how the cache deals with a write cycle. The 2 common write policies areWrite-Throughand Write-Back. In Write-Back policy, the cache behav

PLEASE MAY YOU ASSIST ME WITH SAMPLE CODES FOR PROGRAMING A FIRE ALARM MINI PROJECT

write shell to calculate basic salary from given .

A/D conversion: Basic tasks: (a) Write a program that will read and display the analog voltage on pin PE7 approximately once every second. (b) Write a program that will read and d

Difference between div and idiv