SH7708 datasheet(35/633 Pages) RENESAS

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2.1.3

System Registers

System registers can be accessed by the LDS and STS instructions. When an exception occurs, the

contents of the program counter (PC) are saved in the saved program counter (SPC). The SPC

contents are restored to the PC by the RTE instruction used at the end of the exception handling.

There are four system registers, as follows.

• Multiply and accumulate high register (MACH)

• Multiply and accumulate low register (MACL)

• Procedure register (PR)

• Program counter (PC)

The system register configuration is shown in figure 2.4.

System Registers

Multiply and Accumulate High and Low Registers

(MACH/L)

Store the results of multiply-and-accumulate operations.

Its contents are undefined after a reset.

Procedure Register (PR)

Stores the return address for exiting a subroutine

procedure.

Its contents are undefined after a reset.

Program Counter (PC)

Indicates the address four addresses (two instructions)

ahead of the currently executing instruction. Initialized

to H'A0000000 by a reset.

MACH

MACL

Figure 2.4 System Registers

2.1.4

Control Registers

Control registers can be accessed in privileged mode using the LDC and STC instructions. The

GBR register can also be accessed in user mode. There are five control registers, as follows:

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