CHAPTER 3 CPU FUNCTION
User’s Manual U12688EJ4V0UM00
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3.2.2 System register set
System registers control the status of the CPU and hold interrupt information.
Table 3-2. System Register Numbers
No.
System Register Name
Usage
Operation
0
EIPC
1
EIPSW
Status saving register during
interrupt
These registers save the PC and PSW when a
software exception or interrupt occurs. Because only
one set of these registers is available, their contents
must be saved when multiple interrupts are enabled.
2
FEPC
3
FEPSW
Status saving register during
NMI
These registers save the PC and PSW when an NMI
occurs.
4
ECR
Interrupt source register
If an exception, maskable interrupt, or NMI occurs,
this register will contain information referencing the
interrupt source. The higher 16 bits of this register
are called FECC, to which the exception code of the
NMI is set. The lower 16 bits are called EICC, to
which the exception code of the exception/interrupt is
set.
Refer to Figure 3-2.
5
PSW
Program status word
The program status word is a collection of flags that
indicate the program status (instruction execution
result) and CPU status.
Refer to Figure 3-3.
16
CTPC
17
CTPSW
Status saving register during
CALLT execution
If the CALLT instruction is executed, this register
saves the PC and PSW.
18
DBPC
19
DBPSW
Status saving register during
exception trap
If an exception trap is generated due to detection of
an illegal instruction code, this register saves the PC
and PSW.
20
CTBP
CALLT base pointer
This is used to specify the table address and
generate the target address.
6 to 15
21 to 31
Reserved
To read/write these system registers, specify the system register number indicated by a system register load/store
instruction (LDSR or STSR instruction).
Figure 3-2. Interrupt Source Register (ECR)
31
0
ECR
FECC
EICC
After reset
00000000H
16 15
Bit Position
Bit Name
Function
31 to 16
FECC
Fatal Error Cause Code
Exception code of NMI (refer to Table 7-1 Interrupt List)
15 to 0
EICC
Exception/Interrupt Cause Code
Exception code of exception/interrupt (refer to Table 7-1 Interrupt List)
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