Panasonic MN103S

Chapter 2
CPU Basics
Data Formats II - 9
2.4 Data Formats
Data types can be processed in the four types of bit, byte, halfword and word data. Byte data, halfword data and
word data can be handled as signed and unsigned data. The sign bit is MSB.
The data in the memory must be aligned data. In other words, the two bits on the LSB side of addresses storing
word data must be "00" (addresses which are a multiple of 4), and the LSB of addresses storing halfword data
must be "0" (addresses which are a multiple of 2).
Byte and bit placement conforms with the Little Endian format. Therefore, the address of the byte data on the
MSB side of halfword data is the LSB side byte data address + 1, and the address of the byte data on the MSB side
of word data is the LSB side byte data address + 3. The bit number for bit data starts at 0 on the LSB and
increases towards the MSB.
Table:2.4.1 Data Types
Figure:2.4.1 Little Endian Format
Data type Contents
Bit data Bit data
Byte data
Unsigned 8-bit data
Signed 8-bit data (sign bit: MSB)
Halfword data
Unsigned 16-bit data
Signed 16-bit data (sign bit: MSB)
Word data
Unsigned 32-bit data
Signed 32-bit data (sign bit: MSB)
MSB LSB
Address in the memory
Word data
Bit No. 31 24 23 16 15 8 7 0
4n(4n+1)(4n+2)(4n+3)
Most significant byte
Least significant byte
Upper halfword
Lower halfword
Halfword data
Most significant byte
Least significant byte
Byte data