Filter
Top Products
118
Chapter 5 CPU Registers
2.Dedicated Registers
2.3 TBR: Table-base Register
Table-base register (TBR) consists of 32 bits.
Figure 2-7 Bit Structure of Table-base Register (TBR)
Table-base register holds head address of vector table used for EIT processes.
Vector address is made by adding offset value specified in TBR and EIT each.
2.4 RP: Return Pointer
Return pointer (RP: Return Pointer) consists of 32 bits.
Figure 2-8 Bit Structure of Return Pointer (RP)
Return pointer (RP) holds addresses returned from sub routines.
Upon executing CALL, PC values are set in this RP.
Upon executing RET, RP data are set in this PC.
2.5 SSP: System Stack Pointer
System stack pointer (SSP) is used for the pointer which receives EIT and indicates stack to save/return data for return
operation.
System stack pointer (SSP) consists of 32 bits.
Figure 2-9 Bit Structure of System Stack Pointer (SSP)
When S flag is “0”, it works as R15. You can explicitly specify SSP.
Upon generating EIT, it is used for the pointer which specifies the stack to save PS and PC.
During the EIT process, this pointer reduces the value by 8, and adds 8 to the value during the return from EIT by
executing RETI instruction.
System stack pointer (SSP) works as general-purpose register R15 when S flag within CCR is “0”.
31
[Initial value]
TBR 000FFC00
H
0
31
[Initial value]
RP XXXXXXXX
H
0
31
[Initial value]
SSP 00000000
H
0