CHAPTER 3 CPU FUNCTION
49
User’s Manual U15195EJ5V0UD
3.2.2
System register set
System registers control the status of the CPU and hold interrupt information.
To read/write these system registers, specify a system register number indicated below using the system register
load/store instruction (LDSR or STSR instruction).
Table 3-2. System Register Numbers
Operand Specification
No. System
Register
Name
LDSR Instruction
STSR Instruction
0
Status saving register during interrupt (EIPC)
Note 1
{
{
1
Status saving register during interrupt (EIPSW)
Note 1
{
{
2
Status saving register during NMI (FEPC)
{
{
3
Status saving register during NMI (FEPSW)
{
{
4
Interrupt source register (ECR)
×
{
5
Program status word (PSW)
{
{
6 to 15
Reserved number for future function expansion (operations that access
these register numbers cannot be guaranteed).
×
×
16
Status saving register during CALLT execution (CTPC)
{
{
17
Status saving register during CALLT execution (CTPSW)
{
{
18
Status saving register during exception/debug trap (DBPC)
{
Note 2
{
Note 2
19
Status saving register during exception/debug trap (DBPSW)
{
Note 2
{
Note 2
20
CALLT base pointer (CTBP)
{
{
21 to 31
Reserved number for future function expansion (operations that access
these register numbers cannot be guaranteed).
×
×
Notes 1.
Because this register has only one set, to allow multiple interrupts, it is necessary to save this register
by program.
2.
Access is only possible during the period from when the DBTRAP instruction is executed to when the
DBRET instruction is executed.
Caution Even if bit 0 of EIPC, FEPC, or CTPC is set to 1 with the LDSR instruction, bit 0 will be ignored
when the program is returned by the RETI instruction after interrupt servicing (because bit 0 of
the PC is fixed to 0). When setting the value of EIPC, FEPC, or CTPC, use an even value (bit 0 =
0).
Remark
{
: Access allowed
×
: Access prohibited
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