System Registers - Hitachi SH7750 series Hardware Manual

Saved status register, SSR (32 bits, privilege protection, initial value undefined): The current
contents of SR are saved to SSR in the event of an exception or interrupt.
Saved program counter, SPC (32 bits, privilege protection, initial value undefined): The
address of an instruction at which an interrupt or exception occurs is saved to SPC.
Global base register, GBR (32 bits, initial value undefined): GBR is referenced as the base
address in a GBR-referencing MOV instruction.
Vector base register, VBR (32 bits, privilege protection, initial value = H'0000 0000): VBR is
referenced as the branch destination base address in the event of an exception or interrupt. For
details, see section 5, Exceptions.
Saved general register 15, SGR (32 bits, privilege protection, initial value undefined): The
contents of R15 are saved to SGR in the event of an exception or interrupt.
Debug base register, DBR (32 bits, privilege protection, initial value undefined): When the
user break debug function is enabled (BRCR.UBDE = 1), DBR is referenced as the user break
handler branch destination address instead of VBR.
2.2.5

System Registers

Multiply-and-accumulate register high, MACH (32 bits, initial value undefined)
Multiply-and-accumulate register low, MACL (32 bits, initial value undefined)
MACH/MACL is used for the added value in a MAC instruction, and to store a MAC instruction
or MUL operation result.
Procedure register, PR (32 bits, initial value undefined): The return address is stored in PR in a
subroutine call using a BSR, BSRF, or JSR instruction, and PR is referenced by the subroutine
return instruction (RTS).
Program counter, PC (32 bits, initial value = H'A000 0000): PC indicates the instruction fetch
address.
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