Renesas M32R-FPU - Manual (Page 21)

1
1-13 M32R-FPU Software Manual (Rev.1.01)
1.6.2 Data Format
(1) Data format in a register
The data sizes in the M32R-FPU registers are always words (32 bits).
When loading byte (8-bit) or halfword (16-bit) data from memory into a register, the
data is sign-extended (LDB, LDH instructions) or zero-extended (LDUB, LDUH
instructions) to a word (32-bit) quantity before being loaded into the register.
When storing data from a register into a memory, the 32-bit data, the 16-bit data on
the LSB side and the 8-bit data on the LSB side of the register are stored into
memory by the ST, STH and STB instructions, respectively.
Rn
b0 b31
< load >
byte
Rn
b0 b31
halfword
Rn
b0 b31
word
sign-extention (LDB instruction) or
zero-extention (LDUB instruction)
from memory
(LDB, LDUB instruction)
< store >
Rn
b0 b31
byte
Rn
b0 b31
halfword
Rn
b0 b31
word
to memory (STB instruction)
to memory (STH instruction)
to memory (ST instruction)
from memory (LDH, LDUH instruction)
from memory (LD instruction)
24
16
24
16
sign-extention (LDH instruction) or
zero-extention (LDUH instruction)
Figure 1.6.2 Data Format in a Register
CPU PROGRAMMING MODEL
1.6 Data Format