
3.5.8  System Control Instructions
Table 3-16 describes the 12 system control instructions.
Table 3-16   System Control Instructions
Instruction
System
control
Size
—
—
Function
Generates a trap exception with a specified vector number.
Generates a trap exception if the V bit is set to “1” when 
the instruction is executed.
Returns from an exception-handling routine.
FP 
→
 @–SP;  SP 
→
 FP;  SP + #IMM 
→
 SP
Creates a stack frame.
FP 
→
 SP;  @SP+ 
→
 FP
Deallocates a stack frame created by the LINK instruction.
Causes a transition to the power-down state.
(EAs) 
→
 CR
Moves immediate data or general register or memory 
contents to a specified control register.
CR 
→
 (EAd)
Moves control register data to a specified general register 
or memory location.
CR 
∧
 #IMM 
→
 CR
Logically ANDs a control register with immediate data.
CR 
∨
 #IMM 
→
 CR
Logically ORs a control register with immediate data.
CR 
⊕
 #IMM 
→
 CR
Logically exclusive-ORs a control register with immediate 
data.
PC + 1 
→
 PC
No operation.  Only increments the program counter.
TRAPA
TRAP/VS
RTE
LINK
—
—
UNLK
—
SLEEP
LDC
—
B/W*
STC
B/W*
ANDC
B/W*
ORC
B/W*
XORC
B/W*
NOP
—
*
 The size depends on the control register.
When using the LDC and STC instructions to stack and unstack the BR, CCR, TP, DP, and EP
control registers in the H8/500 family, note the following point.
H8/500 hardware does not permit byte access to the stack. If the LDC.B or STC.B assembler
mnemonic is coded with the @R7 + (@SP+) or @–R7 (@–SP) addressing mode, the stack-
pointer addressing mode takes precedence and hardware automatically performs word access.
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