
RCPU
REFERENCE MANUAL
ADDRESSING MODES AND INSTRUCTION SET SUMMARY
For More Information On This Product,
Go to: www.freescale.com
MOTOROLA
4-65
Table 4-33
summarizes the time base (TBL/TBU) register encodings to which
user-level access read access (using the
mftb
instruction) is permitted.
Writing to the time base is permitted at the supervisor privilege level only and is ac-
complished with the
mtspr
instruction (see
4.7.2 Move to/from Special Purpose
Register Instructions
) or the
mttb
simplified mnemonic (see
E.8 Simplified Mne-
monics for Special-Purpose Registers
).
4.8 Memory Synchronization Instructions
Memory synchronization instructions can control the order in which memory oper-
ations are completed with respect to asynchronous events and the order in which
memory operations are seen by other processors and by other mechanisms that
access memory.
The synchronize (
sync
) instruction delays execution of subsequent instructions
until all previous instructions have completed (i.e., all internal pipeline stages and
instruction buffers have emptied), all previous memory accesses are performed
globally, and the
sync
or
eieio
operation is broadcast onto the external bus inter-
face. This set of conditions is referred to as execution serialization (or simply seri-
alization).
The enforce in-order execution of I/O (
eieio
) instruction serializes load/store in-
structions. No load or store instruction following
eieio
is issued until all loads and
stores preceding
eieio
have completed execution.
The instruction synchronize (
isync
) instruction causes the RCPU to halt instruction
fetch until all instructions currently in the processor have completed execution, i.e.,
all issued instructions as well as the pre-fetched instructions waiting to be issued.
This condition is referred to as fetch serialization.
Table 4-32 Move from Time Base Instruction
Name
Mnemonic
Operand
Syntax
Operation
Move from
Time Base
mftb
r
D,TBR
The TBR field denotes either the time base lower (TBL) or time base
upper (TBU), encoded as shown in
Table 4-33
. The contents of the
designated register are copied to
r
D.
Table 4-33 User-Level TBR Encodings
Decimal
Value in rD
SPR[0:4
]
SPR[5:9]
Register
Name
Description
268
0b01100 01000
TBL
Time base lower (read only)
269
0b01101 01000
TBU
Time base upper (read only)
F
Freescale Semiconductor, Inc.
n
.