MR

The CM register whose contents are to be modified. This can be:

	NOTE: CM registers can not be modified when the user initially entered Debug in NM (nmdebug).

The NM register whose contents are to be modified.

	NOTE: NM registers can not be modified when the user initially entered Debug in CM (cmdebug). Modifying PC modifies PCOF and PCSF. It sets PCOB to PCOF+4 and to PCSF. The original priv bits are retained. That is, when PC is modified, the priv bits are unaffected.

To fully understand the use and conventions for the various registers, refer to the Precision Architecture and Instruction Reference Manual(09740-90014) and Procedure Calling Conventions Reference Manual (09740-90015). (These may be ordered as a set with Part Number 09740-64003.) The procedure calling conventions manual is of particular importance for understanding how the language compilers utilize the registers to pass parameters, return values, and hold temporary values. The following tables list the NM registers available within System Debug. Many registers have aliases through which they may be referenced. Alias names in italics are not available in System Debug.

Access rights abbreviations are listed below. PM indicates that privileged mode (PM) capability is required.

The following registers are known as the General Registers.

The following registers are pseudo registers. They are not defined in the Precision Architecture, but are terms used in the Procedure Calling Conventions document and by the language compilers. They are provided for convenience. They are computed based on stack unwind information. They may not be modified.

The following registers are known as the Space Registers. They are used for short pointer addressing:

The following registers are known as the Control Registers. They contain system state information:

	NOTE: the Precision Architecture and Instruction Reference Manual (09740-90014) refers to the PC (program counter) registers as the IA (instruction address) registers. This manual will use the PC mnemonic when referring to the IA registers.

The following registers are floating-point registers. If a machine has a floating-point coprocessor board, these values are from that board. If no floating-point hardware is present, the operating system emulates the function of the hardware, in which case these are the values from floating-point emulation.

The new value for the register can optionally be supplied on the command line. If the new value was omitted, Debug displays the old value, and prompts for the new value. To retain the original value, just hit return.

When a register is modified, the actual machine registers are not changed until the process is resumed. That is, the new value is recorded and takes effect when Debug is exited using the CONTINUE or EXIT commands. Furthermore the value is applied only to the PIN being debugged. This is true of all but several special registers that are expected to remain constant during the life of MPE XL. The list of these registers follows:

When one of these registers is modified, the new value takes effect immediately. Since these registers are global across all processes, all other users are affected by the change.