CODEWITHSUNDEEP
assemblylc3
user1017593
user1017593

Reputation: 21

In LC-3 assembly language, how do I convert these commands to machine code?

For one of my classes I need to write an LC-3 program in machine code and I can't seem to find the machine codes for the commands that have a period for them:

.ORIG
.END
.BLKW

etc

Does anyone know what they are? I have all of the commands done, for example: AND R2, R2, #0 --> 0101 010 010 1 00000

However I can't find what the first four bits for the .ORIG, .END, .BLKW commands are anywhere online.

Upvotes: 1

Views: 4264

Answers (1)

Carl Norum
Carl Norum

Reputation: 225042

I'm not familiar with your particular dialect, but in most assembly languages, keywords starting with a . aren't instruction mnemonics but assembler directives. In your case, it looks like possibly .ORIG means the start of a program and .END the end. .BLKW seems like a memory filling operation of some kind.

Edit: I did a google search and came up with this presentation. It says that .ORIG describes where to place the following block in memory. For example .ORIG 0x3000 would set the next instruction at address 0x3000. .END, as I mentioned above, describes the end of the program. .BLKW means "block word" and is used to reserve space for use as an array, for example.

In all cases, there aren't any specific machine codes for these directives. For .ORIG, just write out the following opcodes or data at the specified location. .END won't show up in the machine code at all, and .BLKW means you can just copy the specified bytes directly from the assembly program into machine code.

Upvotes: 3

Related Questions