SH7021 datasheet(38/509 Pages) RENESAS

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RENESAS17

MACL

(sign extended)

MACH

Multiply and accumulate (MAC) registers

high and low (MACH, MACL): Store the

results of multiply and accumulate opera-

tions. MACH is sign-extended when read

because only the lowest 10 bits are valid.

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

Initial Value

General register

R0–R14

Undefined

R15 (SP)

Value of the stack pointer in the vector address table

Control register

Bits I0-I3 are 1111(H'F), reserved bits are 0, and other

bits are undefined

GBR

Undefined

VBR

H'00000000

System register

MACH, MACL, PR

Undefined

Value of the program counter in the vector address

table

2.2

Data Formats

2.2.1

Data Format in Registers

bits) or a word (16 bits), it is sign-extended into a long word when stored into a register (figure

2.4).

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