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MPC603e & EC603e RISC Microprocessors User's Manual
MOTOROLA
2.3.5.4 External Control Instructions
The external control instructions allow a user-level program to communicate with a special-
purpose device. The MMU translation of the EA is not used to select the special-purpose
device, as it is used in most instructions such as loads and stores. The EA is used instead as
an address operand that is passed to the device over the address bus. Four other signals (the
burst and size signals on the 60x bus) are used to select the device; these four signals output
the 4-bit resource ID (RID) field that is located in the EAR register. Executing these
instructions when MSR[DR] = 0 causes a programming error, and the physical address on
the bus is undefined. Executing these instructions to a direct-store segment causes a DSI
exception. The external control instructions are listed in Table 2-35.
2.3.6 PowerPC OEA Instructions
The PowerPC OEA includes the structure of the memory management model, supervisor-
level registers, and the exception model.
2.3.6.1 System Linkage Instructions
This section describes the system linkage instructions (see Table 2-36). The
sc
instruction
is a user-level instruction that permits a user program to call on the system to perform a
service and causes the processor to take an exception. The Return from Interrupt (
rfi
)
instruction is a supervisor-level instruction that is useful for returning from an exception
handler.
2.3.6.2 Processor Control Instructions—OEA
Processor control instructions are used to read from and write to the condition register
(CR), machine state register (MSR), and special-purpose registers (SPRs), and to read from
the time base register (TBU or TBL).
Table 2-35. External Control Instructions
Name
Mnemonic
Operand Syntax
External Control In Word Indexed
eciwx
r
D
,r
A
,r
B
External Control Out Word Indexed
ecowx
r
S
,r
A
,r
B
Table 2-36. System Linkage Instructions
Name
Mnemonic
Operand Syntax
System Call
sc
—
Return from Interrupt
rfi
—