E.1.3.1 Machine State Register (Msr) - Motorola MPC8240 User Manual

• Miscellaneous registers
— The time base facility (TB) for writing. The TB is a 64-bit register pair that can
be used to provide time of day or interval timing. It consists of two 32-bit
registers—time base upper (TBU) and time base lower (TBL). The TB is
incremented once every four sys_logic_clk cycles.
— Decrementer (DEC). The DEC register is a 32-bit decrementing counter that
provides a mechanism for causing a decrementer exception after a
programmable delay. The DEC is decremented once every four sys_logic_clk
cycles.
— External access register (EAR). This optional register is used in conjunction with
the eciwx and ecowx instructions. While the PowerPC architecture specifies that
the low-order six bits of the EAR (bits 26–31) are used to select a device, the
603e and MPC8240 only implement the low-order 4 bits (bits 28–31). Note that
the EAR register and the eciwx and ecowx instructions are optional in the
PowerPC architecture and may not be supported in all PowerPC processors that
implement the OEA.

E.1.3.1 Machine State Register (MSR)

The machine state register (MSR) is shown in Figure E-10.
0000 0000 0000 0
0
Table E-8 shows the bit definitions for the MSR.
Reset
Bit(s) Name
Value
0–12 — 0
13 POW 0
TGPR
POW
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Figure E-10. Machine State Register (MSR)
Table E-8. MSR Bit Settings
Reserved
Power management enable (603e-specific)
0 Power management disabled (normal operation mode)
1 Power management modes enabled (doze, nap, or sleep mode)
This bit controls the programmable power modes only; it has no effect on dynamic power
management (DPM). MSR[POW] may be altered with an mtmsr instruction only. Also,
when altering the POW bit, software may alter only this bit in the MSR and no others with
the same instruction. The mtmsr instruction must be followed by a context-synchronizing
instruction.
Appendix E. Processor Core Register Summary
ILE EE PR FP ME FE0 SE BE FE1 0
Description
PowerPC Register Set
Reserved
IP IR DR 00 RI LE
E-13