Loading Multiple Base Registers

1
Loading Multiple Base Registers
2
Programmer Responsibilities

• Tell the assembler which registers to choose when
  creating base/displacement addresses
• X DS CL5 gt C008
  (BDDD)
• Do this with USING
• USING ,R12
• Load the base register with the correct address

3
Loading a Single Register

• Address
• X1000 BASR R12,R0
• USING ,R12
• X1002 ...

4
Why is this Incorrect?

• Address
• USING ,R12
• X1000 BASR R12,R0
• X1002 ...

5
Loading Multiple Registers

• Address
• X1000 BASR R12,R0
• USING ,R12,R11,R10
• X1002 LA R10,2048
• LA R11,2048(R12,R10)
• LA R10,2048(R11,R10)
• Remember that X1000 4096
• X800 2048

6
Direction

• It would be helpful to understand the terms
  Domain and Range as they relate to USINGs.
• Also, read about the DROP directive