Datasheet
47
2.1.3 System Registers
System registers consist of four 32-bit registers: high and low multiply and accumulate registers
(MACH and MACL), the procedure register (PR), and the program counter (PC). The multiply
and accumulate registers store the results of multiply and accumulate operations. The procedure
register stores the return address from the subroutine procedure. The program counter stores
program addresses to control the flow of the processing. Figure 2.3 shows a system register.
MACL
PR
PC
MACH
31 0
0
0
31
31
Multiply and accumulate (MAC)
registers high and low (MACH,
MACL): Stores the results of
multiply and accumulate operations.
Procedure register (PR): Stores
a return address from a
subroutine procedure.
Program counter (PC): Indicates
the fourth byte (second instruction)
after the current instruction.
Figure 2.3 System Registers
2.1.4 Initial Values of Registers
Table 2.1 lists the values of the registers after reset.
Table 2.1 Initial Values of Registers
Classification Register Initial Value
General registers R0–R14 Undefined
R15 (SP) Value of the stack pointer in the vector address table
Control registers SR Bits I3–I0 are 1111 (H'F), reserved bits are 0, and other
bits are undefined
GBR Undefined
VBR H'00000000
System registers MACH, MACL, PR Undefined
PC Value of the program counter in the vector address table