gtpp2m0rProgramming Standards

Register Usage

The following gives the TPF system perspective on register usage, but not the application perspective. Registers R0-R7 are saved for an application by the TPF system.

Registers Reserved for the Application Program Interface

 Register 8 = R8 = 
TYPE E PROGRAM BASE REGISTER

 Register 9 = R9 = 
ENTRY CONTROL BLOCK BASE REGISTER

Registers Reserved for Control Program Use

 Register 11 = R11 = 
CONTROL PROGRAM BASE REGISTER (fixed)

 Register 12 = R12 = 
CONTROL PROGRAM BASE REGISTER (fixed)

 Register 13 = R13 = 
CONTROL PROGRAM STACK REGISTER

Registers R10, R11, R12, R13, R14, and R15 are not guaranteed across macro calls.