
2
2-7
32192/32195/32196 Group Hardware Manual
Rev.1.10 REJ09B0123-0110 Apr.06.07
CPU
2.4 Accumulator
The Accumulator (ACC) is a 56-bit register used for DSP function instructions.
The accumulator is handled as a 64-bit register when accessed for read or write. When reading data from the
accumulator, the value of bit 8 is sign-extended. When writing data to the accumulator, bits 0 to 7 are ignored.
The accumulator is also used for the multiply instruction “MUL,” in which case the accumulator value is destroyed
by instruction execution.
Use the MVTACHI and MVTACLO instructions for writing to the accumulator. The MVTACHI and MVTACLO
instructions write data to the high-order 32 bits (bits 0–31) and the low-order 32 bits (bits 32–63), respectively.
Use the MVFACHI, MVFACLO and MVFACMI instructions for reading data from the accumulator. The
MVFACHI, MVFACLO and MVFACMI instructions read data from the high-order 32 bits (bits 0–31), the low-order
32 bits (bits 32–63) and the middle 32 bits (bits 16–47), respectively.
Upon exiting the reset state, the value of accumulator is undefined.
15
b0
16
7 8
31 32
47 48
b63
ACC
(Note 1)
Read range of MVFACMI instruction
Write and read ranges of MVTACLO
and MVFACLO instructions
Write and read ranges of MVTACHI
and MVFACHI instructions
Note 1: When read, bits 0 to 7 always show the sign-extended value of the value of bit 8. Writing to this
bit field is ignored.
2.5 Program Counter
The Program Counter (PC) is a 32-bit counter that retains the address of the instruction being executed. Since
the M32R FPU instruction starts with even-numbered addresses, the LSB (bit 31) is always "0."
Upon exiting the reset state, the value of PC is H’0000 0000.
b0
b31
0
PC