Problem Session 3 for ECE 109 / CSCI 255

This problem session is about LC-3/human instruction decoding and execution.

Start by decoding and executing two binary programs stored in a spreadsheet.

There are many things to remember.

• LD and LDR make one memory access.
• ST and STR make one memory access.
• LDI makes two memory accesses.
• STI makes two memory accesses, a read and a write.
• LEA makes no memory accesses.
• The PC is one more than the address of the current instruction.
• Immediate and offset fields are sign-extended.
• HALT is TRAP x25.
• HALT is not TRAP #25.
• Avoid unnecessary conversions between hexadecimal and decimal.
• Many LC-3 words will contain data, not instructions.
• LDR does not add to a register.